A new iron mailbox was installed at the entrance of Guanghua Street, 50cm long, 40cm wide, and 70cm high. How many square centimeters of iron sheet is needed to make this mailbox?
光华街口装了一个新的铁皮邮箱，长50cm，宽40cm，高70cm．做这个邮箱至少需要多少平方厘米的铁皮？
<gadget id="calculator">50 * 40</gadget>
<output>2_000</output>

<gadget id="calculator">50 * 70</gadget>
<output>3_500</output>

<gadget id="calculator">40 * 70</gadget>
<output>2_800</output>

<gadget id="calculator">2_000 + 3_500 + 2_800</gadget>
<output>8_300</output>

<gadget id="calculator">8_300 * 2</gadget>
<output>16_600</output>

<result>16_600</result>