If a product is sold at the fixed price, it can make a profit of 100 yuan. If it is sold at a discount of 20%, it can still make a profit of 20%. What is the cost of this product?
某种商品按定价出售可获利100元，若打八折出售仍可获利20%，这件商品的成本是多少元．
<gadget id="calculator">1.2 - 0.8</gadget>
<output>0.4</output>

<gadget id="calculator">80 / 0.4</gadget>
<output>200</output>

<result>200</result>