The orchard buys a batch of apples and divides them into three grades according to the quality. The best apples are the first grade, priced at 3.6 yuan per kilogram; the second is the second grade apples. The price per kilogram is 2.8 yuan; the last is the price of third-class apples at 2.1 yuan per kilogram. The ratio of the number of these three kinds of apples is 2:3:1. If these three kinds of apples are sold together, what is the appropriate price per kilogram?
果园收购一批苹果，按质量分为三等，最好的苹果为一等，每千克售价3.6元；其次是二等苹果．每千克售价2.8元；最次的是三等苹果每千克售价2.1元．这三种苹果的数量之比为2：3：1．若将这三种苹果混在一起出售，每千克定价多少元比较适宜．
<gadget id="calculator">3.6 * 2</gadget>
<output>7.2</output>

<gadget id="calculator">2.8 * 3</gadget>
<output>8.4</output>

<gadget id="calculator">2.1 * 1</gadget>
<output>2.1</output>

<gadget id="calculator">7.2 + 8.4 + 2.1</gadget>
<output>17.7</output>

<gadget id="calculator">2 + 3 + 1</gadget>
<output>6</output>

<gadget id="calculator">17.7 / 6</gadget>
<output>2.95</output>

<result>2.95</result>