Find the surface area of each of the following cuboids: the length and width are both 6 cm, and the height is 3.4 cm.
求下面各长方体的表面积：长和宽都是6厘米，高3.4厘米．
<gadget id="calculator">6 * 6</gadget>
<output>36</output>

<gadget id="calculator">6 * 3.4</gadget>
<output>20.4</output>

<gadget id="calculator">36 + 20.4 + 20.4</gadget>
<output>76.8</output>

<gadget id="calculator">76.8 * 2</gadget>
<output>153.6</output>

<result>153.6</result>