For a trapezoid, the upper base is 8 cm long. If the upper base is increased by 3 cm, it will be exactly equal to the lower base. Its two waists are 5 cm and 4 cm long respectively. What is the perimeter of the trapezoid in cm?
一个梯形，上底长8厘米，如果把它的上底增加3厘米，那么正好与下底相等，它的两腰长分别是5厘米、4厘米，这个梯形的周长是多少厘米？
<gadget id="calculator">3 + 8</gadget>
<output>11</output>

<gadget id="calculator">8 + 11 + 5 + 4</gadget>
<output>28</output>

<result>28</result>