A piece of trapezoidal glass has an upper base of 1.4m, a lower base of 2.8m, and a height of 1.2m. If the price per square meter of glass is 68 yuan, how much does it cost to buy this piece of glass?
一块梯形玻璃，它的上底1.4m，下底2.8m，高1.2m，如果每平方米玻璃价钱是68元，买这块玻璃要用多少元钱？
<gadget id="calculator">1.4 + 2.8</gadget>
<output>4.2</output>

<gadget id="calculator">1.2 / 2</gadget>
<output>0.6</output>

<gadget id="calculator">4.2 * 0.6 * 68</gadget>
<output>171.36</output>

<result>171.36</result>