Designers want to introduce a new line of bookcases. They want to make at least 100 bookcases, but not more than 2000 of them. They predict the cost of producing x bookcases is (). Assume that () is a differentiable function. Which of the following must they do to find the minimum average cost, ()=()/x

(1) find the points where ()=0 and evaluate () there

(2) compute () to check which of the critical points in (I) are local maxima

(3) check the values of at the endpoints of its domain.

A group of designers wants to introduce a new line of bookcases. They want to make at least 100 bookcases, but not more than 2000 of them. They predict the cost of producing x bookcases is ()C(x). Assume that ()C(x) is a differentiable function. Which of the following must they do to find the minimum average cost, ()=()A(x)=C(x)x?

(1) find the points where ()=0A(x)=0 and evaluate ()A(x) there

(2) compute ()A(x) to check which of the critical points in (I) are local maxima

(3) check the values of A at the endpoints of its domain.

(a) 1 only

(b) 1 and 2 only

(c) 1 and 3 only

(d) 1, 2, and 3.