 Dear students, today we will discuss demand per labour and we will discuss it with the help of profit maximization approach. In our last four modules, we discussed the production function. Production function actually, can be economy, productive capacity could determine. So we discussed this, that why the function of capital and labour and technology. So productive capacity, doh tara se determine hotiye, number one quantities of inputs, that how much labour is being utilized and how much the amount of capital is being utilized. For second, how effectively these factors of production are being utilized. So labour demand curve could discuss, we will start from a firm's behavior, with the help of firm, we will discuss that how a firm decides the number of workers to be employed. So to keep our analysis simple, we are making certain assumptions. First assumption is that we are keeping capital stock and the state of technology fixed. Actually we are doing the short run analysis. For short run analysis, it is quite reasonable that we assume that capital stock change. Because capital stock change takes a lot of time. Capital stock can be changed in two ways, number one with the help of new investment, this will increase the existing capital stock and number two depreciation. When we are using capital stock, over the time it depreciates or the actual amount of capital stock decreases. But these two things are very slowly moving, that is why for a short run analysis, we can reasonably assume that capital stock is fixed. Similarly, state of technology, this means effectiveness. And we can reasonably assume that in short run, state of technology also does not change. So firstly, our assumption is change in capital stock and change in technology. We are assuming that these changes are zero, these are constant over the short period. Secondly, we have already discussed that now why the function of only labor, why the function of n or margin product of labor, that is first derivative of y with respect to n is positive. That whenever we will increase the units of labor, our total output will increase and it will increase at decreasing rate. This means that first derivative is positive and the second derivative is negative. So these assumptions we have discussed today. So second assumption is that our firm is working in a perfect competition. Perfect competition means that all the firms are alike, identical and firms are price takers, input market and output market. In both the markets, the firm cannot influence the wage rate. This market determines that the firm has to accept it. Similarly, in the output market, the firm cannot influence the price of its output. It is also determined by the interaction of the demand and supply forces. So in both the markets, the input market and the output market, the firm is a price taker. The firm cannot set the price on its own and cannot change it. Secondly, the objective of the firm is profit maximization. The firm can have other objectives but we are assuming that the firm is working under profit maximization. So we define the profit function. Pi is the profit or we define it and when we put these three lines, it means this is the definition actually, identity. So profit is defined as P y, P is the price of the output, y is the amount of the output. So P y you can call it, it is the total revenue minus W n and we know that our A key factor of production that is labor. So n is the units of labor and W is the wage rate. So second your term had W n, this is you can say this is the total cost or your first term had P y, this is the total revenue. So the difference is simply the profit. So this is just the definition of profit and we want to maximize our profit. So once our choice variable is A key, the firm that we can choose is the number of workers. So choice variable is n, so firm wants to maximize its profit and choice variable is the number of workers. So we will see the reference of how the profit will be maximized and how the firm will decide how many workers we have to hire. Thank you very much.