ComGas, the Cambridge Power Company, Charges Its Customers $\$ 6.78$ A Month, Plus an Additional

Multiple Choice

ComGas, the Cambridge power company, charges its customers $\$ 6.78$ a month, plus an additional $\$ 1.00$ per therm up to 32 therms and $\$ 0.66$ per therm above 32 therms. (A therm is a unit of gas supplied.) Let $C(x)$ be the monthly cost in dollars for using $x$ therms. Which of the following is the formula for $C$ ?

A) $C(x) =\left\{\begin{array}{lc}6.78+1.00 x, & 0 \leq x \leq 32 \\ 6.78+0.66 x, & x>32\end{array}\right.$
B) $C(x) =\left\{\begin{array}{cc}6.78+1.00 x, & 0 \leq x \leq 32 \\ 38.78+0.66 x, & x>32\end{array}\right.$
C) $C(x) =\left\{\begin{array}{cc}6.78+1.00 x, & 0 \leq x \leq 32 \\ 6.78+0.66(x-32) , & x>32\end{array}\right.$
D) $C(x) =\left\{\begin{array}{cc}6.78+1.00 x, & 0 \leq x \leq 32 \\ 38.78+0.66(x-32) , & x>32\end{array}\right.$