In order to encourage residents to save water, the water company stipulates that each household will be charged 1.2 yuan per ton for 15 tons or more (including 15 tons) of water per month, and 2.4 yuan per ton for the part exceeding 15 tons. Huanhuan’s family used 18 tons of water last month. How much water should Huanhuan’s family pay last month?
为鼓励居民节约用水，自来水公司规定：每户每月用水15吨以(含15吨)按每吨1.2元收费，超过15吨的部分按每吨2.4元收费．欢欢家上月用水18吨，欢欢家上月应缴水费多少元？
<gadget id="calculator">1.2 * 15</gadget>
<output>18</output>

<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<gadget id="calculator">2.4 * 3</gadget>
<output>7.2</output>

<gadget id="calculator">18 + 7.2</gadget>
<output>25.2</output>

<result>25.2</result>