Noel is a computer repairman. To fix a computer, he charges a customer $40 per hour, plus a fixed fee of $15 for the service call, as represented by the function f(x) = 40x + 15. In the equation, what is represented by the variable “x”? A. the amount Noel charged per hour

B. the number of hours Noel worked

C. the fixed fee for the service call

D. the total cost of the repair job