There is a rectangular water tank with a length of 15 cm and a width of 20 cm. A stone is placed in it. The height of the water before it is put in is 6 cm. After the stone is completely submerged in the water, the water level rises by 4 cm. Find the volume of the stone.
有一个长方形的水缸，长15厘米，宽20厘米，放进一块石头，放入之前水的高度是6厘米，石头全部沉入水后，水面升高4厘米，求这块石头的体积．
<gadget id="calculator">15 * 20 * 4</gadget>
<output>1_200</output>

<result>1_200</result>