What of the following gives the best estimate for the marginal cost, in dollars, to produce the 40th cupcake?

Question

Function C is the cost for the guy's store to produce cupcakes of a certain type where c(x) is the cost, in dollars, to make x of the cupcakes. the function m is defined as m(x)=c(x+1)-c(x) gives the marginal cost, in dollars, to produce cupcake number x+1. What of the following gives the best estimate for the marginal cost, in dollars, to produce the 40th cupcake?

A) C(39)/39

B) C(40)/40 - C(39)/39

C) C'(39)

D) C'(40) - C' (39) 

Answer 1

D) C(40) - C (39)  is approximate marginal cost to produce 40th item.

C(40) - C(39) ≈ C'(39)

Answer is C)