An office with a length of 8 meters, a width of 6 meters, and a height of 2.8 meters needs to be painted. It is known that the doors and windows are 42 square meters in total. How big is the area that needs to be painted (the floor is not painted)?
一间长8米、宽6米、高2.8米的办公室需要粉刷，已知门窗共42平方米，需要粉刷的面积有多大(地面不刷)？
<gadget id="calculator">8 * 6</gadget>
<output>48</output>

<gadget id="calculator">8 * 2.8</gadget>
<output>22.4</output>

<gadget id="calculator">6 * 2.8</gadget>
<output>16.8</output>

<gadget id="calculator">22.4 + 16.8</gadget>
<output>39.2</output>

<gadget id="calculator">39.2 * 2</gadget>
<output>78.4</output>

<gadget id="calculator">48 + 78.4 + (-42)</gadget>
<output>84.4</output>

<result>84.4</result>