If ((a)/12) is a true fraction, what is the sum of all possible outcomes of a that are even numbers.
若((a)/12)是真分数，则a的所有可能的结果中为偶数的值之和为多少．
<gadget id="calculator">2 + 4 + 6 + 8 + 10</gadget>
<output>30</output>

<result>30</result>