5 kilograms of first-grade toffee, 2.8 yuan per kilogram, 3 kilograms of second-grade toffee, 2.2 yuan per kilogram, 2 kilograms of third-grade toffee, 3.6 yuan per kilogram, if these toffees are mixed and sold, how much is the average per kilogram?
一级奶糖5千克，每千克2.8元，二级奶糖3千克，每千克2.2元，三级奶糖2千克，每千克3.6元，把这些奶糖混合以后出卖，平均每千克多少元？
<gadget id="calculator">2.8 * 5</gadget>
<output>14</output>

<gadget id="calculator">2.2 * 3</gadget>
<output>6.6</output>

<gadget id="calculator">3.6 * 2</gadget>
<output>7.2</output>

<gadget id="calculator">14 + 6.6 + 7.2</gadget>
<output>27.8</output>

<gadget id="calculator">5 + 3 + 2</gadget>
<output>10</output>

<gadget id="calculator">27.8 / 10</gadget>
<output>2.78</output>

<result>2.78</result>