Use the Five-Step Strategy for Solving Word Problems to Find $\$ 12$

Use the five-step strategy for solving word problems to find the number or numbers described in the following
exercise.
-Sergio's internet provider charges its customers $\$ 12$ per month plus 3 c per minute of on-line usage. Sergio received a bill from the provider covering a 2 -month period and was charged a total of $\$ 35.70$ . How many minutes did he spend on-line during that period? (Round to the nearest whole minute, if necessary.)

A) The number of minutes is 390 .
B) The number of minutes is $439 .$
C) The number of minutes is 772 .
D) The number of minutes is 39 .