There is a circular flower bed with a base diameter of 8 meters. Now a path with a width of 2 meters is to be built around the flower bed. If the investment is 50 yuan per square meter, how much is the investment to build this path?
有一个底面直径是8米的圆形花坛，现在要在这个花坛周围修建一条宽2米的小路，如果每平方米要投资50元，修成这条小路要投资多少元？
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

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

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

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

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<gadget id="calculator">113.04 - 50.24</gadget>
<output>62.8</output>

<gadget id="calculator">50 * 62.8</gadget>
<output>3_140</output>

<result>3_140</result>