Chapter 2.2, Problem 41E

(a)

To determine

Whether the average rate of change of cost greater from $x=a$ to $x=b$ or from $x=b$ to $x=c$

(b)

To determine

Whether the number of units $d$ need to saitsfy $d<b$ or $d>b$ for the average rate of change of cost from $x=a$ to $x=d$ to be greater than that from $x=a$ to $x=b$.