A sporting goods store bought a batch of basketballs, divided into first-class products and second-class products. The purchase price of second-class products is 20% cheaper than that of first-class products. According to the principle of high quality and high price, first-class products are priced at a profit margin of 20%. , The second-grade product is priced at 15% of the profit, and the first-grade product is 28 yuan more expensive than the second-grade product. How much is the purchase price of each first-grade basketball?
某体育用品商店进了一批篮球，分一级品和二级品，二级品的进价比一级品便宜20%，按优质优价的原则，一级品按20%的利润率定价，二级品按15%的利润定价，一级比二级品每个篮球贵28元，问一级品篮球每个进价是多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(1/5) * (3/20)</gadget>
<output>3/100 = around 0.03</output>

<gadget id="calculator">(3/100) - 1 - (3/20)</gadget>
<output>-28/25 = around -1.12</output>

<gadget id="calculator">1 + (1/5) + (1/5) + (-28/25)</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">28 / (7/25)</gadget>
<output>100</output>

<result>100</result>