Question

A power company calculates a person's monthly bills from the number of kilowatt-hours (kWh), x, used.

Answer 1

Evaluate b(300). Since 300>200, use the second rule:

$\begin{gathered} b(300)=0.1(300-200)+30 \\ =0.1(100)+30 \\ =10+30 \\ =40 \end{gathered}$

Therefore, the bill for a person who uses 300KWh in a month is $40.