A rectangular test field has a circumference of 40 meters and a width of 8 meters. What is its area?
一块长方形试验场，周长40米，宽8米，它的面积是多少？
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<gadget id="calculator">12 * 8</gadget>
<output>96</output>

<result>96</result>