4x + 7 Find the total cost function C(x) (in thousands of dollars) if the marginal cost (in thousands of dollars per unit) at a production level of x units is C'(x) = x (0 S x $4), and fixed costs are $50,000 (c(0) = 50) Which of the following explains how to find C(x), the total cost function if the marginal cost at a production level of x units is C'(x)? O A. To find the total cost function, evaluate the indefinite integral of the marginal cost and apply the initial conditions (c(0) = 50) Therefore, C(x) = (Type an exact answer) O B. To find the total cost function, evaluate the derivative of the marginal cost and apply the initial conditions (c(0) = 50) Therefore, C(x) =