When multiplying two numbers, if one factor increases by 3, the product increases by 60; if the other factor decreases by 4, the product decreases by 100. What is the original product of the two factors?
两个数相乘，如果一个因数增加3，积就增加60；如果另一个因数减少4，积就减少100，原来两个因数的积是多少．
<gadget id="calculator">25 * 20</gadget>
<output>500</output>

<result>500</result>