After the semester starts, the school plans to repaint the school conference room. It is known that the accounting room is 8 meters long, 7 meters wide, and 3 meters high. The total area of doors and windows is 18 square meters. If 0.4 kg of lime is used per square meter, please help the school calculate How many kilograms of lime should be prepared?
学期开学后，学校准备重新粉刷学校会议室，已知会计室长8米、宽7米、高3米，门窗面积合计18平方米，如果每平方米用0.4千克石灰，请你帮学校计算一下应准备多少千克石灰？
<gadget id="calculator">8 * 7</gadget>
<output>56</output>

<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">24 + 21</gadget>
<output>45</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<gadget id="calculator">90 - 18</gadget>
<output>72</output>

<gadget id="calculator">56 + 72</gadget>
<output>128</output>

<gadget id="calculator">128 * 0.4</gadget>
<output>51.2</output>

<result>51.2</result>