Marginal analysis is very important in business and economics. In the following example below, a company manufactures fuel tanks for cars. The total weekly cost in dollars of producingxtanks is given by

C(x) = 10,000 + 90x - 0.05x²

Explain how you would:

(A) Find the marginal cost function.

(B) Find the marginal cost at a production level of 400 tanks per week.

(C) Interpret the results of part (B).

(D) Find the exact cost of producing the 401st item.