Which rate is the best deal for making copies at the copy store?

a.
$3.15 for 50 copies

b.
$3.70 for 60 copies

c.
$4.50 for 75 copies

d.
$1.25 for 20 copies

To determine the best deal, calculate for the cost per copy in each of the choices. Calculations are shown below.
 
A. $3.15 / 50 copies = $0.063 / copy

B. $3.70 / 60 copies = $0.0617 / copy

C. $4.50 / 75 copies = $0.06 / copy

D. $1.25 / 20 copies = $0.0625 / copy

By choices the least cost per copy among the choices, the answer is letter C.