Answer
a. $c(75)=90,$
$c(90)=105,$
$c(100)=100,$
$c(105)=105$.
b.For order less than $100$, by paying for shipping cost of $15$ will sometimes end up costing more than for paying the order of greater than $100$.
Work Step by Step
$C(x)=$ $\begin{cases}
x+15&if&x\lt100\\
x&if&x\geq100
\end{cases}$
a. Since $75\lt100$ $c(75)=75+15=90,$
Since $90\lt100$ $c(90)=90+15=105,$
Since $100\geq100$ $c(100)=100,$
Since $105\geq100$ $c(105)=105$.
b. For order less than $100$, by paying for shipping cost of $15$ will sometimes end up costing more than for paying the order of greater than $100$.
