The school wants to build a school building. Its length is 9 meters and its width is 6 meters. In order to lay the foundation of the wall, a trench with a width of 0.5 meters and a depth of 0.5 meters needs to be dug. How many cubic meters of soil should be dug in total?
学校要盖一个校舍，它的长是9米，宽是6米，为了打墙基，需要挖宽0.5米，深0.5米的沟，一共要挖多少立方米的土？
<gadget id="calculator">6 - 0.5 - 0.5</gadget>
<output>5</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">10 + 18</gadget>
<output>28</output>

<gadget id="calculator">28 * 0.5 * 0.5</gadget>
<output>7</output>

<result>7</result>