Aplumber 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?