For a trapezoid, if the upper base is increased by 4 cm and the lower base is decreased by 4 cm, it becomes a square with side length 10 cm. What is the area of the trapezoid in square centimeters?
一个梯形，如果上底增加4cm，下底减少4cm，就成为一个边长是10cm的正方形，这个梯形的面积是多少平方厘米．
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">10 + 4</gadget>
<output>14</output>

<gadget id="calculator">6 + 14</gadget>
<output>20</output>

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

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<result>100</result>