A publisher can sell x thousand copies of a monthly sports magazine at the price of p = 5-x/100 dollars. The monthly publishing cost, C can be modeled by 160 C(x) = 800- 200x - 0.05x² a. determines the equation that expresses income. b. determine the equation that expresses the profits. c. Calculate the marginal profit for a volume of 30,000 magazines. d. Calculate the maximum profit.