A store sells a schoolbag. If each one sells for 150 yuan, then 60% of the selling price is the purchase price, and 40% of the selling price is the money earned. Now we need to conduct promotional activities to ensure that a schoolbag can earn a lot of money. How should the discount be determined if the discount is less than 30 yuan?
商店卖一种书包，如果每个售价为150元，那么售价的60%是进价，售价的40%就是赚的钱，现在要搞促销活动，为保证一个书包赚的钱不少于30元，应该怎样确定折扣？
<result>30</result>