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

The function $b(x)=\left\{\begin{array}{ll}0.15 x, & x \leq 200 \\ 0.10(x-200)+30, & x> 200\end{array}\right.$ determines the bill.
How much is the bill for a person who uses $700 \mathrm{kWh}$ in a month?

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Answer

$\boxed{80}$ is the bill for a person who uses 700 kWh in a month.

Steps

Step 1 ：Given the function b(x) = $\begin{cases} 0.15x, & x \leq 200 \\ 0.10(x-200)+30, & x>200 \end{cases}$, we need to find the value of b(700).

Step 2 ：Since 700 > 200, we use the second part of the function: $0.10(700-200)+30$.

Step 3 ：Calculating the result: $0.10(500)+30 = 50+30 = 80$.

Step 4 ：$\boxed{80}$ is the bill for a person who uses 700 kWh in a month.