Use abc to indicate the waiting time of three people respectively. When abc is the smallest, the total time is the least.

The first a

The second b

The third c

It can be known that no matter how the sequence changes, the waiting time of the third one remains unchanged, even if 10+ 12+8=30 minutes. Then we only need to consider the shortest time of the first and second, the first is 8 minutes, the second is 8+ 10 minutes, and the total time is 8+ 18+30=56 minutes.