What is the perimeter of a rectangular flower bed with a length of 5 meters and a width of 4 meters?
一个长方形花坛，长5米，宽4米，周长是多少．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

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

<result>18</result>