Xiaoqing bought 4 AA batteries, paid 10 yuan, and got back 1.6 yuan. How much is the price of each AA battery? (List the equations and write out the relationship)
小青买4节五号电池，付出10元，找回1.6元，每节五号电池的价格是多少元？(列方程并写出关系式)
<gadget id="calculator">10 - 1.6</gadget>
<output>8.4</output>

<gadget id="calculator">8.4 / 4</gadget>
<output>2.1</output>

<result>2.1</result>