a.) Revenue = price * quantity = px = -1/20x^2 + 1060x
R(x) = -1/20x^2 + 1060x.
b.) Profit = Revenue - Cost = R(x) - C(x) = -1/20x^2 + 1060x - 120x - 5000
P(x) = -1/20x^2 + 940x - 5000
c.) For maximum profit, dP/dx = 0
-1/10x + 940 = 0
1/10x = 940
x = 940 * 10 = 9,400
x = 9,400
Maximum profit = P(9400) = -1/20(9400)^2 + 940(9400) - 5000 = $4,413,000
d.) The price to be charged for maximum profit = -1/20(9400) + 1060 = $590