The original area of a school playground is 2800m**2, but due to expansion, the width is increased from 40m to 50m, and the length remains unchanged. How much m**2 does the expanded playground area increase from the original?
某校操场原有面积2800m**2，因扩建，把宽从40m增加到50m，长不变．扩建后的操场面积比原来增加多少m**2？
<gadget id="calculator">2_800 / 40</gadget>
<output>70</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<gadget id="calculator">70 * 10</gadget>
<output>700</output>

<result>700</result>