What characterises the point of maximum on a Total Revenue graph?

Question

What characterises the point of maximum on a Total Revenue graph?

(a) the point where the second derivative is positive

(b) the point where the gradient is parallel to the vertical (upright) axis

(c) the point at which the gradient is zero (d) the point at which the derivative is equal to 1

Answer 1

c)

the point of maximum revenue is when marginal revenue = 0

derivative of TR = MR = 0

Revenue function is an upside down U, which is concave down with 2nd derivative <0

a) and d) are incorrect. b) sounds like an undefined derivative