Racetracks quote the approximate odds against each horse winning on a large board called a tote board. The odds quoted on a tote board for a race with four horses are as follows.

Horse                              Number Odds

2 . . . . . . . . . . . . . . . . . . . . . . 15 : 1

3 . . . . . . . . . . . . . . . . . . . . . .   1 : 1

4 . . . . . . . . . . . . . . . . . . . . . .   3 : 1

5 . . . . . . . . . . . . . . . . . . . . . . 13 : 3

Determine the probability of each horse winning the race.