Answer
(a) The actual cost for a 90 minute call is:
Penny Saver \$0.84
Most Minutes \$0.715
USA Card \$1.15
(b) Use the actual cost from (a) to find the unit cost.
Penny Saver \$0.009/min
Most Minutes \$0.008/min
USA Card \$0.013/min
The best buy is Most Minutes.
Work Step by Step
(a) To find the actual total cost, add the connection fee to the per minute charge for 90 minutes.
Penny Saver $0.39 + (90)(0.005)$ = $0.39+0.45$ = 0.84
Most Minutes $0.49 + (90)(0.0025)$ = $0.49+0.225$ = 0.715
USA Card $0.25 + (90)(0.01)$ = $0.25+0.90$ = 1.15
(b) Use the actual cost from (a) to find the unit cost.
Penny Saver $\frac{0.84}{90 min}$ = $\frac{0.84\div90}{90\div90 min}$ = $\frac{0.009}{1 min}$ = 0.009/min
Most Minutes $\frac{0.715}{90 min}$ = $\frac{0.715\div90}{90\div90 min}$ = $\frac{0.008}{1 min}$ = 0.008/min
USA Card $\frac{1.15}{90 min}$ = $\frac{1.15\div90}{90\div90 min}$ = $\frac{0.013}{1 min}$ = 0.013/min
