Jake hires a septic system contractor to dig trenches for his new septic tank. The cost to hire the contractor is a fixed cost of $160 plus an additional $70 per hour. Which expression below describes the average cost of an x-hour job?

A160x+70/x dollars per hour

Bx/70x+160 dollars per hour

C70x+160/x dollars per hour

D160+70/x dollars per hour