Draw the largest semicircle and the largest circle in the rectangle. Given that the perimeter of the rectangle is 60 cm, find the area of the blank part.
在长方形里画一个最大的半圆和一个最大的圆，已知长方形的周长是60厘米，求空白部分的面积．
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">18 * 12</gadget>
<output>216</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">3.14 * 36</gadget>
<output>113.04</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 3.14 * 36</gadget>
<output>56.52</output>

<gadget id="calculator">216 - 113.04 - 56.52</gadget>
<output>46.44</output>

<result>46.44</result>