classroom is 8 meters long, 6 meters wide, and 4 meters high. Now the roof and walls need to be painted, excluding doors, windows and blackboards, the area is 20 square meters. If the material cost is 2 yuan per square meter, how much is the total material cost for painting this classroom?
一间教室长8米，宽6米，高4米，现在要粉刷屋顶和四壁，除去门窗和黑板面积20平方米．如果每平方米需材料费2元粉刷这间教室共需材料费多少元？
<gadget id="calculator">8 * 6</gadget>
<output>48</output>

<gadget id="calculator">8 * 4 * 2</gadget>
<output>64</output>

<gadget id="calculator">6 * 4 * 2</gadget>
<output>48</output>

<gadget id="calculator">48 - 20</gadget>
<output>28</output>

<gadget id="calculator">48 + 64 + 28</gadget>
<output>140</output>

<gadget id="calculator">140 * 2</gadget>
<output>280</output>

<result>280</result>