(w,k)
that is amount of women and children lefton original side
ok, first realize you must get children across first because who will row the boat back
first trip: 10min, 2 children across, (3,1)
2nd trip: 20min, 1 kid cross back (3,2)
3rd trip: 30min, 2 kids cross (3,0)
4th trip: 40 min, 1 kid cross baack (3,1)
5th trip: 50 min, 1 woman cross (2,1)
6th trip: 60 min, 1 kid cross back (2,2)
7th trip: 70 min, 1 woman cross (1,2)
8th trip: 80 min, 1 kid cross back (1,1)
9th trip: 90 min, 1 woman cross (0,1)
10th trip: 100min, 1 kid cross back (0,2)
11th trip: 110 min, 2 kids cross back (0,0)
min time is 110 mins or 1hr 50min