In order to encourage residents to save water, the water company stipulates that each user will be charged 2.4 yuan per ton for water consumption within 15 tons (including 15 tons) per month; if the water exceeds 15 tons, the excess tonnage will be charged at 3 yuan per ton. Zhang Hong’s family uses 19 tons of water this month. Please help Zhang Hong do the math. How much does his family have to pay for water this month?
为鼓励居民节约用水，自来水公司规定：每用户每月用水15吨以内(含15吨)，按每吨2.4元收费；超过15吨的，其超过的吨数按每吨3元收费．张红家这个月用水19吨，请你帮张红算一算，这个月他家要交水费多少元？
<gadget id="calculator">2.4 * 15</gadget>
<output>36</output>

<gadget id="calculator">19 - 15</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">36 + 12</gadget>
<output>48</output>

<result>48</result>