Write the Word or Phrase That Best Completes Each Statement

Essay

Write the word or phrase that best completes each statement or answers the question.
-A gas company has the following rate schedule for natural gas usage in single-family residences:
$\begin{array}{cl}\text { Monthly service charge } & \$ 8.80 \\\text { Per therm service charge } & \\\text { 1st } 25 \text { therms } & \$ 0.6686 / \text { therm } \\\text { Over } 25 \text { therms } & \$ 0.85870 / \text { therm }\end{array}$
What is the charge for using 25 therms in one month?
What is the charge for using 45 therms in one month?
Construct a function that gives the monthly charge C for x therms of gas.