The manager of the company notifies A, B, and C to go to the office to talk. It takes 15 minutes for A to finish talking, 12 minutes for B to finish talking, and 18 minutes for C to finish talking. How to arrange the order of three people talking, so that the three people spend the least number of minutes. (Talk in order of B, A, C)
公司经理通知A、B、C三人去办公室谈话．A谈完要15分钟，B谈完要12分钟，C谈完要18分钟．怎样安排三人谈话顺序，使三人花的时间最少是多少分钟．(按B、A、C顺序谈话)
<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">12 + 15 + 18</gadget>
<output>45</output>

<gadget id="calculator">12 + 27 + 45</gadget>
<output>84</output>

<result>84</result>