 So, students last lecture may be, we have read about production function. So, if you recall, we have read that production function is basically a relationship among output and the factor of production. So, this is the mathematical expression, which relates the amount of output with the amount of inputs. So, in this y is the output, real output produced in a given time period and a is the number which measures the overall productivity. So, a represents the state of technology, the state of knowledge, efficiency, the factors of production, how effectively they are being used. And k is the capital stock, our quantity of capital used in that period and similarly n is the number of workers employed in that period. So, f, f is the symbol used to show the functional relationship between factors of production and output. Students technology a, which represents the state of knowledge go, technology go, effectiveness go, how efficiently effectively factors of production are being translated into output. So, this a, which is production function may different forms may have been introduced. For example, first form is this one, which is called as a neutral technological progress. This means that any improvement in technology will affect the marginal products of labour and capital in the same way. For example, if technology 10 percent, if there is an improvement in it, then marginal product of labour, b 10 percent will increase and marginal product of capital b 10 percent. So, this affects both of them in the same way. That is why we say that this is a neutral introduction of technology. The other is capital augmenting. In this, we will see that we are multiplying a with k. So, multiplicative form a into k. So, this means that any improvement in technology will affect only the marginal product of capital and labour will not be affected by this. For example, if technology 10 percent changes, then this marginal product of capital will just increase, marginal product of labour will not increase. So, in this context, we always say that capital augmenting technological progress. The other form is labour augmenting. So, you will see that in this, we have multiplied technology a with n. So, any improvement in technology will affect only the marginal product of labour. Capital will not affect this. So, I am recapping these three differences. That technology can be introduced in three types of production functions. The first one is the neutral way. The second is capital augmenting. And the third one is the labour augmenting. And I have explained this in the previous lecture. So, we will see that this is a marginal product of labour. Capital augmenting and the third one is the labour augmenting. And I have explained that neutral means that in technology, improvement will affect both of them in one way. Capital augmenting will only affect the marginal product of capital and labour augmenting will only affect labour. Another dimension which we can classify production function. You read this in microeconomics. Long-run or short-run production function. So, in long-run production function, all factors of production are variable. So, a can change, k can be changed, and n can be changed. So, we will use this. For example, if we want to discuss returns to scale, return to scale means that if you double all factors of production, then how much output will change? If we want to discuss this, then we will use this kind of long-run production function. Similarly, we will study growth theories and we will use long-run production function. And the second way in which we describe this is short-run production function. In short-run production function, for example, we put k over bar. This means that we are keeping this k constant, n can be changed, and a also assumed in the short-run constant. So, technology is not changing. We have fixed capital stock just by changing the value of n. We are seeing how output will change. So, this short-run production function. We will use this specifically in business cycle theories. We will use short-run production function chain or laugh variable proportion or factor productivity for short-run production function. Thank you very much.