A batch of products can be harvested by 28 people in 25 days. After 5 days of production, this task must be completed 10 days in advance. How many people should be added?
一批产品，28人25天可以收割完，生产5天后，此项任务要提前10天完成，应增加多少人．
<gadget id="calculator">28 * 25</gadget>
<output>700</output>

<gadget id="calculator">28 * 5</gadget>
<output>140</output>

<gadget id="calculator">700 - 140</gadget>
<output>560</output>

<gadget id="calculator">25 - 5 - 10</gadget>
<output>10</output>

<gadget id="calculator">560 / 10</gadget>
<output>56</output>

<gadget id="calculator">56 - 28</gadget>
<output>28</output>

<result>28</result>