Lan Lan has a building block. The upper and lower bases of the building block are two identical trapezoids. The upper base of the trapezoid is 2 cm, the lower base is 4 cm, and the height is 3 cm. What is the total area of the top and bottom of the block in square centimeters?
兰兰有一块积木，积木的上、下底面是两个完全相同的梯形，梯形的上底是2厘米，下底是4厘米，高是3厘米．这块积木上、下底面的总面积是多少平方厘米？
<gadget id="calculator">2 + 4</gadget>
<output>6</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">6 * (3/2) * 2</gadget>
<output>18</output>

<result>18</result>