 Consumer behavior and the topic that we are going to study it is the well-behaved preferences. What we mean by the well-behaved preferences? That is the basic assumption under that topic of the indifference curve that the indifference curve should be when the consumer is having the well-behaved preferences then the indifference curve will follow the proper shape or the axioms. So, there are the 1, 2, 3 different factors where we require to be followed by the indifference curve. And number one is that if the preference of a consumer will be monotonic or the consumer is going to perform monotonically. So, what we mean by the monotonically? Monotonically is a very simple concept. The other way round we will say a consumer will always like to have more of a good to the less of a good. Commodities. Now, if we look at this point, then when he trade-off from one place to the trade-off of the other bundle, then definitely if we look at the approach of this one indifference curve, if we look at the curve and it goes to the higher level, then the higher level indifference curve will be having more amount of a bundle x1, x2 or at the same time may have the amount of y1, y2 he or the she will prefer towards higher bundle and the higher level of the indifference curve. In this way, when the consumer will move from one indifference curve to the higher level indifference curve and then to other indifference curve, he will reach towards the proper point of satiation or the bridge point. So, in this way we can say that the property of satiation or the property of monotonicity, they both are equally indispensable for following the rules of indifference curve for each other. Without the presence of one, the other cannot be expressed. So, in the economics, we can say the subject where the everyone will be satiated in their consumption of every good but for a very little time and for a very particular point. Then the third concept related to this that is coming that is the convexity. So, in convexity, we will say that it is related to the shape of the indifference curve. So, when we say that in consumer behavior, consumers will be having a well behaved preference curve if those preferences they will be exhibited in the form of convexity and when we say the convexity, it means it will be negatively sloped towards the origin or it can be in the form of negatively sloped or inward sloping. So, because in this form we can say when we move from point A to B or B to C, the consumer will be under the theory of parity optimality or the welfare, he or the she will be willing to sacrifice one commodity to attain the other commodity. He will not be in a form that he will gain one commodity and he will gain the other commodity as well. These conditions will only be followed when the consumer has to move to the higher level of the indifference curve but on the same indifference curve, this quality of convexity, it requires that the consumer is just going to trade one commodity in lieu of the other commodity. So, if a consumer is having a bundle of the two commodities in which we can say that he is having 50 units of one commodity and the 50 units of the other commodity, so as per counting, he is having the 100 units. Now, if he wants the 60 units of a commodity, then definitely he has to sacrifice some units of the other commodity. If the both goods will be perfect substitutes, he will sacrifice in the same amount 10 and the 10. If that will be limited substitution, he will also sacrifice but that substitution rate may differ. So, this property of convexity, it will determine the shape of the proper well-behaved preferences to have the properties of the indifference curve. Now, in the diagram, we can explain with a very simple way that if the consumer is having two points of consumption bundle, here it is the indifference curve of the consumer and on this indifference curve, we are having just two bundles depicted in this diagram, but these two are just in the diagram, otherwise we can have many other combinations on this indifference curve and these all combinations are equally good for the consumer and the consumer can trade off between any of these or all other bundles. And the convexity is explained in a manner that if any two points that are extreme to this curve, if they both are joined by a line and all the other matter and all other points, they fall below this point or on the left side, we will say that that indifference curve or the utility curve is exhibiting the convexity because it is downward sloping. So, here that this point of Z, if we include, it means at this point consumer is having half of these bundles and half of these bundles and now if he has to trade off, he has to come at this point suppose, so then he has to move from Z to this point and for which he has to sacrifice this much amount of X1 to gain this much amount of X2 and if he has to move up to this point that we can say point Q, so to move from Z to Q, consumer is again sacrificing amount of X, he is gaining point X1 this much, but they are sacrificing this much amount of X2, so the property of convexity, it maintains the property of indifference curve. So, the preferences, they are strictly convex when we utilize the mixtures of the good, not only the one, so in indifference curve approach or all other problems that we are going to explain related to consumer behavior, we used to express not only from one single commodity, rather by the mixture of the goods or the bundles because that shows the natural tendency of the consumer to exhibit its expression of the preference. Now, if we take the example of anything that is explained here in this one diagram, we can say in daily life we see that a consumer, if he is having all the bundles available on this indifference curve and this is the point where we can see that he is having the better bundle or the optimal bundle because that might be having a tendency to the budget line. So, if it is like this, there are many other indifference curve, they can be available to the consumer in this manner and if we draw a series of indifference curve like this and like this. So, over the map of this indifference curve, if we are going to draw the optimal point and we are going to join this, we can have the movement like this, that on right side or the left, from that optimal point, if consumer will move towards on the right side and the right side, his level of betterment is going to increase and if from this point he is moving towards left and left, it means the consumer is now on the worst bundles or his welfare is going to reduce. So, in different positions, we can say that the consumer either moving from leftward this point to the leftward. So, on the same indifference curve, consumer will move from left to up and if right to right and down, but if on different indifference curve, then the consumer will move towards the right and then towards left. So, this movement gives the consumer various levels of the welfare that he may attain from his previous point of the satiation or the previous point of the welfare.