Hard Math problem!!!?

Question

The cost in dollars to print n copies of a magazine is given by the formula, C=-0.000025n^2 + 0.325n

a) Find the average rate of the cost of printing the magazine using the interval from 100 copies to 200 copies.

i try this for part a -

C(100)= -0.000025(100)^2 + 0.325(100)
= -0.25+32.5
= 32.25

c(200) = -0.000025(200)^2 + 0.325(200)
= -1 + 65= 64

so then I try this

64- 32.25/ 200-100

but the answers says---- $.25/copy how do they get this

b) Find the average rate of the cot of rnting the magazine using the interval from 200 copies to 300 copies.

answer = $.20/copy

What is the marginal cost( the cost of printing one extra copy)
after 100 papers have been printed? ( the cost of printing the 101 st copy. answer= $.27

Answer 1

You found the average cost, not the average rate of cost. In part (b) you define "marginal cost" and that definition indicates that you are not using calculus. Consequently, I don't know how to answer rate questions without using calculus, so I cannot help you.