Two classmates, Zhang Xiao and Wei Han, went to the store to buy the same exercise book. Zhang Xiao bought 6 copies, and Wei Han bought 4 copies. Wei Han paid 80 cents less than Zhang Xiao. How much is each exercise book?
张晓和魏含两个同学相约到商店买同样的练习本，张晓买了6本，魏含买了4本，魏含比张晓少付了8角钱，每本练习本多少钱？
<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">0.8 / 2</gadget>
<output>0.4</output>

<result>0.4</result>