Final answer:
After integrating the marginal profit function and applying the initial condition, the profit function is P(x) = 15x^4 + 45x^3 - 50. To find the profit from selling 400 pounds of Brie cheese, plug x = 4 into the profit function to get $6670.
Step-by-step explanation:
To solve for the profit function, we need to integrate the given marginal profit function P'(x) = x(60x^2 + 90x), given that the profit is -$50 when no cheese is sold. By integrating the given function concerning x and using the initial condition, we find the indefinite integral:
∫ P'(x) dx = ∫ x(60x^2 + 90x) dx
P(x) = 15x^4 + 45x^3 + C
We apply the initial condition P(0) = -50 to find the constant of integration C:
-50 = 15(0)^4 + 45(0)^3 + C ⇒ C = -50
Now the profit function is:
P(x) = 15x^4 + 45x^3 - 50
For part (b), to find the profit from selling 400 pounds of cheese, we use the profit function with x = 4 (since x is measured in hundreds of pounds):
P(4) = 15(4)^4 + 45(4)^3 - 50
P(4) = 15(256) + 45(64) - 50
P(4) = 3840 + 2880 - 50
P(4) = 6670
Thus, the profit from selling 400 pounds of Brie cheese is $6670.