Suppose there are 100 identical competitive firms operating in the Frisbee industry. Each firm's total cost function is: TC=100+10q+2q^2.

4a) Calculate each firm's short run supply curve.

4b) Calculate the industry supply curve.

4c) If the price of a Frisbee is $18, at what level of output do firms maximize profits in the short run?

4d) Given your answer to part 4c, should these firms produce or shut down?