The edge length of a cube glass tank is 20 cm, and the depth of water stored in it is 8 cm. A piece of iron with a length of 20 cm, a width of 5 cm, and a thickness of 4 cm is completely submerged in the water. How deep is the water in the tank at this time?
正方体玻璃缸棱长20厘米，里面存储的水深8厘米，把一块长20厘米、宽5厘米、厚4厘米的铁块全部浸没在水中，这时缸中水深多少厘米？
<gadget id="calculator">20 * 5 * 4</gadget>
<output>400</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">400 / 400</gadget>
<output>1</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<result>9</result>