A new iron sheet mailbox was installed at the entrance of Guanghua Street. It is 50cm long, 40cm wide, and 78cm high. How many square meters of iron sheet are needed to make this mailbox?
光华街口装了一个新的铁皮邮箱，长50cm，宽40cm，高78cm，做这个邮箱至少需要多少平方米的铁皮？
<gadget id="calculator">50 * 40</gadget>
<output>2_000</output>

<gadget id="calculator">50 * 78</gadget>
<output>3_900</output>

<gadget id="calculator">40 * 78</gadget>
<output>3_120</output>

<gadget id="calculator">2_000 + 3_900 + 3_120</gadget>
<output>9_020</output>

<gadget id="calculator">2 / 10_000</gadget>
<output>1/5_000 = around 0.0002</output>

<gadget id="calculator">9_020 * (1/5_000)</gadget>
<output>451/250 = around 1.804</output>

<result>451/250 = around 1.804</result>