An investor bought N shares of a company at a price of 75 yuan per share. After that, he sold 60% of them at a price of 120 yuan per share, and sold the rest at a low price of 70 yuan per share on the following day. out. If he obtained a profit of 7,500 yuan from this stock operation, how many shares did he buy?
一投资者以每股75元的价格买了一公司的股票N股，此后，他以每股120元的价格卖掉了60%，剩余的在随后一天又以每股70元的低价卖出．如果他从这次股票操作中获得7500元的利润，那么他买了多少股．
<result>300</result>