Write the Word or Phrase That Best Completes Each Statement

Write the word or phrase that best completes each statement or answers the question.
-An electric company has the following rate schedule for electricity usage in single-family residences: $\begin{array}{llcc}\text { Monthly service charge } & \$ 4.93\\\\\text { Per kilowatt service charge }&\\ \text {1st 300 kilowatts } & \text { \( \$ 0.11589 / \mathrm{kW} \) }\\ \text { Over 300 kilowatts} & \text {\( \$ 0.13321 / \mathrm{kW} \) }\\\end{array}$

What is the charge for using 300 kilowatts in one month?
What is the charge for using 375 kilowatts in one month?
Construct a function that gives the monthly charge C for x kilowatts of electricity.