A classroom is 8 meters long, 6 meters wide, and 4 meters high, and the area of doors and windows is 18 square meters. To paint the walls and ceiling of the classroom, if 0.25 kilograms of lime is used per square meter, how many kilograms of lime will be used in total?
一间教室长8米、宽6米、高4为，门窗面积18平方米．要粉刷教室的四壁和顶棚，如果每平方米用石灰0.25千克，一共要用石灰多少千克？
<gadget id="calculator">6 * 8</gadget>
<output>48</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">48 + 32 + 24</gadget>
<output>104</output>

<gadget id="calculator">104 * 2</gadget>
<output>208</output>

<gadget id="calculator">8 * 6</gadget>
<output>48</output>

<gadget id="calculator">208 - 48 - 18</gadget>
<output>142</output>

<gadget id="calculator">142 * 0.25</gadget>
<output>35.5</output>

<result>35.5</result>