Carolyn paid a mechanic x dollars per hour for ac 5-hour job plus $70 for parts. The total charge was $320. Which equation can be used to determine how much the mechanic charged per hour?

A. 5x = 320 + 70
B. 5x = 320 - 70
C. (70 + 5)x= 320
D. (70 - 5)x = 320