Teacher Zhang bought 4 copies of "Fun Mathematics" and "Story King", paid 20 yuan, and got 7.6 yuan back. Each copy of "Fun Math" is 1.6 yuan, how much is each copy of "Story King"?
张老师买《趣味数学》和《故事大王》各4本，付出20元，找回7.6元．每本《趣味数学》1.6元，每本《故事大王》多少元？
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<result>4</result>