The Beijing Bus Company stipulates that for air-conditioned buses with prefixes 6-9, the fare for using the IC card is 0.8 yuan for driving no longer than 12 kilometers, and the fare is 0.4 yuan for every additional 5 kilometers (if the distance is less than 5 kilometers, it will be charged for 5 kilometers). Taking bus No. 927 and swiping IC card for 2.8 yuan, what is the maximum mileage he can travel on bus No. 927?
北京巴士公司规定；6-9字头空调公交车，行驶不超过12千米使用ⅠC卡票价为0.8元，每增加5千米加价0.4元(不足5千米按5千米收费)某人乘坐927路公交车刷ⅠC卡2.8元，他乘坐927路公交车的里程最多是多少千米．
<gadget id="calculator">2.4 / 0.4</gadget>
<output>6</output>

<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">30 + 12</gadget>
<output>42</output>

<result>42</result>