Xiaoming’s water meter last month read 413 tons, and this month’s reading is 420 tons. The unit price of water is 1.80 yuan. How much is Xiaoming’s total water bill this month?
小明家水表上月读书是413吨，本月读数是420吨，水的单价是1.80元，小明家这个月一共要交水费多少元．
<gadget id="calculator">420 - 413</gadget>
<output>7</output>

<gadget id="calculator">7 * 1.8</gadget>
<output>12.6</output>

<result>12.6</result>