Aunt Li bought 5 kilograms of bananas and 4.2 kilograms of apples for a total of 49 yuan, and 5.6 yuan per kilogram of bananas. Please do the math, how much is an apple per kilogram?
李阿姨买了5千克香蕉和4.2千克苹果一共用了49元，香蕉每千克5.6元．请你算一算，苹果每千克多少元？
<gadget id="calculator">5 * 5.6</gadget>
<output>28</output>

<gadget id="calculator">49 - 28</gadget>
<output>21</output>

<gadget id="calculator">21 / 4.2</gadget>
<output>5</output>

<result>5</result>