A plumber charges a flat fee of $79 to visit a home and examine a clogged drain. The plumber charges an additional $21 per hour spent fixing the drain. The total cost, c (in dollars), for fixing a drain that takes, h hours is given by the following function.
C(h)=79+21h
(a) What is the total cost for fixing a drain that takes 7 hours?
(b) If the plumber charges a total of $310, how many hours did he spend fixing the drain?
