1,200 exercise books with a cost of 0.25 yuan are sold at a price of 40% of the profit. After 80% of the exercise books are sold out, the remaining exercise books are sold at a discount. When all the exercise books are sold out, the profit obtained is 86% of the predetermined profit. How much discount are the remaining exercise books on sale?
成本是0.25元的练习本1200本，按40%的利润定价出售，售完80%后，剩下的练习本打折销售，售完全部练习本，结果获得的利润是预定的86%．剩下的练习本是打几折出售的？
<result>8</result>