A furniture factory makes a cuboid wooden drawer with a length of 5 decimeters, a width of 4 decimeters, and a height of 1 decimeter. How many square decimeters of wooden boards are needed to make such a drawer?
家具厂做一种长5分米，宽4分米，高1分米的长方体木抽屉，做一个这样抽屉至少需多少平方分米的木板？
<gadget id="calculator">4 * 1</gadget>
<output>4</output>

<gadget id="calculator">5 * 1</gadget>
<output>5</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">18 + 20</gadget>
<output>38</output>

<result>38</result>