Answer
a) 119 dollars
b) 77 dollars
c) As the number of bookcases increases, the average cost decreases.
Work Step by Step
$C(x)=\frac{35x+4200}{x}$
a)
$x=50$
$C(x)=\frac{35x+4200}{x}$
$C(50)=\frac{35*50+4200}{50}$
$C(50)=(1750+4200)/50$
$C(50)=5950/50$
$C(50)=119$
b)
$x=100$
$C(x)=\frac{35x+4200}{x}$
$C(100)=\frac{35*100+4200}{100}$
$C(100)=(3500+4200)/100$
$C(100)=7700/100$
$C(100)=77$