A cylindrical container with a bottom radius of 9 cm contains 3.6 cm deep water. A cylindrical iron rod with a bottom radius of 3 cm and a length of 15 cm is vertically inserted into the bottom of the container (the iron rod is not completely submerged) , what is the height of the water surface at this time?
一个圆柱形容器，底面半径9厘米，里面装有3.6厘米深的水，现将一根底面半径3厘米，长15厘米的圆柱形铁棍竖直插入这个容器底部(铁条未被完全淹没)，这时水面的高度是多少？
<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">3.14 * 81 * 3.6</gadget>
<output>915.624</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9 * 3.6</gadget>
<output>101.736</output>

<gadget id="calculator">915.624 + 101.736</gadget>
<output>1_017.36</output>

<gadget id="calculator">3.14 * 81</gadget>
<output>254.34</output>

<gadget id="calculator">1_017.36 / 254.34</gadget>
<output>4</output>

<result>4</result>