1 gallon = 16 cups
Hope it helps you.
You should buy cookies, because .80 x200=160 , which is less than $200
B if you need an explanation just comment
Marginal profit, P(x) = R(x) - C(x)
P(x) = x³ - 5x² + 7x + 10
x³ - 5x² + 7x + 10 = 0
If you solve it, you get x = -0.839 where P(x) is zero
