If it costs 12.4 yuan to buy 3 pencils, 2 rulers, and 4 erasers, and the sum of the unit prices of these three stationery is 4.8 yuan, how much does it cost to buy 4 pencils, 2 rulers, and 6 erasers?
如果买3支铅笔，2把直尺、4块橡皮需要12.4元，且这三样文具的单价之和为4.8元，那么买4支铅笔，2把直尺、6块橡皮需要多少元．
<gadget id="calculator">12.4 - 4.8</gadget>
<output>7.6</output>

<gadget id="calculator">7.6 * 2</gadget>
<output>15.2</output>

<result>15.2</result>