If the circumference of the base of a cylinder is 15.7 decimeters and the height is 3 decimeters, what is its surface area in square decimeters?
一个圆柱的底面周长是15.7分米，高是3分米，它的表面积是多少平方分米．
<gadget id="calculator">15.7 * 3</gadget>
<output>47.1</output>

<gadget id="calculator">15.7 / 3.14 / 2</gadget>
<output>2.5</output>

<gadget id="calculator">2.5 ** 2</gadget>
<output>6.25</output>

<gadget id="calculator">3.14 * 6.25 * 2</gadget>
<output>39.25</output>

<gadget id="calculator">47.1 + 39.25</gadget>
<output>86.35</output>

<result>86.35</result>