The silver part of the disc is a ring, the diameter of the inner circle is 4 cm, and the width of the ring is 4 cm. What is the area of the silver part in square centimeters?
光盘的银色部分是一个圆环，内圆直径是4厘米，环宽是4厘米，银色部分面积是多少平方厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 + 4</gadget>
<output>6</output>

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

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">36 - 4</gadget>
<output>32</output>

<gadget id="calculator">3.14 * 32</gadget>
<output>100.48</output>

<result>100.48</result>