How can the group cross the bridge in 17 minutes?

Question

A group of four people wants to cross bridge. It is dark, and they have to light the path with a torch. No more than two people can cross the bridge simultaneously, and the group has only one torchlight. It takes different time for the people in the group to cross the bridge:

A crosses the bridge in 1 minute,
B crosses the bridge in 2 minutes,
C crosses the bridge in 5 minutes,
D crosses the bridge in 10 minutes.

How can the group cross the bridge in 17 minutes?

Answer 1

1,2 2 mins
return 2 2 mins
5,10 10 mins
retunr 1 1 min
1,2 2 mins
---------------
17 mins
--------------------

Answer 2

 The moves are as follows: 

                 Move                                             Time
        (1) & (2) Cross with Torch                                 2
       (1) Returns with Torch                                      1
       (5) & (10) Cross with Torch                                10
      (2) Returns with Torch                                       2
     (1) & (2) Cross with Torch                                    2
                                                                  17
Alternatively the second move can be (2) returning with the torch, 
the times are the same.