To paint a classroom with a length of 8.5 meters, a width of 6 meters, and a height of 4 meters, the ceiling and walls need to be painted, and the blackboard, doors and windows are 29.2 square meters. The average lime used per square meter is 0.25 kilograms. How many kilograms of lime are needed in total?
粉刷一个长8.5米，宽6米，高4米的教室，需要粉刷天花板和四壁，除去黑板门窗29.2平方米，平均每平方米用石灰0.25千克，一共需要石灰多少千克？
<gadget id="calculator">8.5 * 6</gadget>
<output>51</output>

<gadget id="calculator">8.5 * 4</gadget>
<output>34</output>

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

<gadget id="calculator">34 + 24</gadget>
<output>58</output>

<gadget id="calculator">58 * 2</gadget>
<output>116</output>

<gadget id="calculator">116 - 29.2</gadget>
<output>86.8</output>

<gadget id="calculator">51 + 86.8</gadget>
<output>137.8</output>

<gadget id="calculator">137.8 * 0.25</gadget>
<output>34.45</output>

<result>34.45</result>