(-/8 Points] DETAILS The cost, in thousands of dollars, of airing x television commercials during a sports event is given by C(x) = 20 + 3,000x + 0.07x (a) Find the marginal cost function C'(x). HINT [See Example 1.] C'(x) = Use it to estimate how fast the cost is increasing when x = 4. thousand dollars per television commercial Compare this with the exact cost of airing the fifth commercial. The cost is going up at the rate of $ per television commercial. The exact cost of airing the fifth commercial is $ . Thus, there is a difference of $ (b) Find the average cost function C, and evaluate C(4). HINT [See Example 2.] c(x)= C( 4 ) = thousand dollars per television commercial What does the answer tell you? The average cost of airing the first four commercials is $ per commercial. Need Help? Read It Watch It