The teachers and students of Class 1, Grade 5, paint the classroom by themselves. The length of the classroom is 9 meters, the width is 6 meters, and the height is 4 meters. How many kilograms of lime is used for painting this classroom?
某校五年级1班师生自己动手粉刷教室，教室的长9米，宽6米，高4米，门窗面积占18平方米，要粉刷四周墙壁和顶棚，如果每平方米用白灰0.25千克，粉刷完这一教室共用白灰多少千克？
<gadget id="calculator">9 * 4 * 2</gadget>
<output>72</output>

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

<gadget id="calculator">9 * 6</gadget>
<output>54</output>

<gadget id="calculator">54 - 18</gadget>
<output>36</output>

<gadget id="calculator">72 + 48 + 36</gadget>
<output>156</output>

<gadget id="calculator">0.25 * 156</gadget>
<output>39</output>

<result>39</result>