ECON 302 - What is the firm's Total Cost function

4. (12 total points) Suppose a firm can use either Capital (K) or Labor (L) in a production process. The firms Production function is given by Q = 5L + 15K. The price of Capital is $20 per unit and the price of Labor is $8 per unit.

a) (4 points) What is the firm's Total Cost function?

TC(Q) = ____________________________

b) (8 points) Suppose the firm is producing 30 units of output (Q = 30). Using a graph, draw the firm's isoquant for Q = 30. Also, on the same graph, draw the isocost line associated with the total cost of producing Q = 30. Your graph should be accurate and carefully labeled. Please put the units of Capital (K) on the vertical axis, and the units of Labor (L) on the horizontal axis. Make sure to clearly indicate the cost-minimizing combination of Labor and Capital that the firm should use, and to clearly label both the isocost line and the isoquant.