Assume only one firm in the industry, and that it can charge customers their willingness to pay. Consumers all have the following demand, p = 20 q. Furthermore, assume that the marginal cost of production is $c (where c is a known constant).

(a) Calculate the optimal set of the price(s) and output level.

(b) How will an increase in cost, as represented by an increase in c, affect your answers in part a)?