A certain city stipulates that each household’s monthly water consumption shall not exceed 10 tons (including 10 tons), and the water fee shall be 1.8 per ton; if it exceeds 10 tons (but not exceeding 20 tons), the excess part shall be charged at 2.5 yuan per ton; if more than 20 tons, The excess part is charged at 3.5 yuan per ton. Xiaohua's family used 27 tons of water last month. How much should I pay for the water?
某市规定每户市民每月用水不超过10吨(含10吨)，每吨水收费1.8；超过10吨(但不超过20吨)，超出的部分按每吨2.5元收费；超过20吨，超出的部分按每吨3.5元收费．小华家上月用水27吨，应交水费多少钱？
<gadget id="calculator">1.8 * 10</gadget>
<output>18</output>

<gadget id="calculator">2.5 * 10</gadget>
<output>25</output>

<gadget id="calculator">27 - 20</gadget>
<output>7</output>

<gadget id="calculator">3.5 * 7</gadget>
<output>24.5</output>

<gadget id="calculator">18 + 25 + 24.5</gadget>
<output>67.5</output>

<result>67.5</result>