Which of the following statements is correct? a_ A basic theorem of calculus is that an optimal value for a function can be determined by taking the first derivative of that function, setting it equal to zero, and solving the resulting equation. b A basic theorem of calculus is that if the second derivative of a function is positive when evaluated at the optimal value, the optimal value is a maximum. Cc When the total cost can be expressed as a nonlinear function, there is only one possible break-even point. d The basic economic order quantity formula is derived using regression analysis. e None of the above.ki9