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.