Limin store bought a batch of mosquito coils from a daily miscellaneous company, and then sold them at a price increase of 40% per bag according to the expected net profit. However, when 90% of the mosquito coils are sold at this price, the summer will be over. In order to speed up capital turnover, the store sold all the remaining mosquito coils at a preferential price of 30% off the price. In this way, the actual net profit obtained is 15% less than the expected net profit. According to regulations, regardless of the price at which the mosquito coils are sold, a business tax of 300 yuan must be paid when the batch of mosquito coils is sold out (the tax and the money used to buy the mosquito coils are used as the cost). How much did the Limin store spend to buy this batch of mosquito coils?
利民商店从日杂公司买进一批蚊香，然后按希望获得的纯利润，每袋加价40%定价出售．但是，按这种定价卖出这批蚊香的90%时，夏季即将过去．为加快资金周转，商店以定价打七折的优惠价，把剩余蚊香全部卖出．这样，实际所得纯利润比希望获得的纯利润少了15%．按规定，不论按什么价钱出售，卖完这批蚊香必须上缴营业税300元(税金与买蚊香用的钱一起作为成本)．问利民商店买进这批蚊香用了多少元？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">300 * (3/20)</gadget>
<output>45</output>

<gadget id="calculator">0.4 * (3/20)</gadget>
<output>0.06</output>

<gadget id="calculator">0.06 - 0.042</gadget>
<output>0.018</output>

<gadget id="calculator">45 / 0.018</gadget>
<output>2_500</output>

<result>2_500</result>