The function D(p) gives the number of items that will be demanded when the price is p. The production cost C(x) is the cost of producing x items. To determine the cost of production when the price is $6, you would do which of the following?
a. Evaluate D(C(6)).
b. Evaluate C(D(6)).
c. Solve D(C(x)) = 6.
d. Solve C(D(p)) = 6.