A rectangular parallelepiped is a frame surrounded by 84cm long iron wires. It is known that the length is 11cm, the width is 6cm, and the height is cm.
一个长方体用84cm长的铁丝围成的框架，已知长是11cm，宽是6cm，高是多少cm．
<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<gadget id="calculator">21 - 11 - 6</gadget>
<output>4</output>

<result>4</result>