In April 2009, Peoples Energy had the following rate schedule for natural gas usage in singlefamily residences:
Monthly service charge                    $15.95
Per therm service charge
1st 50 therms                     $0.33606/therm
Over 50 therms                  $0.10580/therm
Gas charge                            $0.3940/therm

(a) What is the charge for using 50 therms in a month?

(b) What is the charge for using 500 therms in a month?

(c) Develop a model that relates the monthly charge C for x therms of gas.

(d) Graph the function found in part (c).