A rectangle has a length of 8 decimeters and a height of 20 decimeters. If it is cut horizontally into 4 small cuboids, the surface area will increase by 240 decimeters. What is the volume of the original rectangle?
一个长方形的长为8分米，高为20分米，如果沿着水平方向把它横切成4个小长方体，表面积就增加了240平方分米，则原来长方形的体积为多少立方分米．
<gadget id="calculator">240 / 6</gadget>
<output>40</output>

<gadget id="calculator">40 * 20</gadget>
<output>800</output>

<result>800</result>