Each roll of the dice is independent of any prior roll. In a three dice game, there are 216 possible rolls ( 6 x 6 x 6).
So, when Alice rolls the dice, her chance of rolling a sum of 13 is based on the fact that in a three dice game, there are 21 ways to roll a total of 13. So, 21/216 = 9.72%
After she rolls the dice, Benny will roll them, and there are 15 ways to roll a sum of 7. So, 15/216 = 6.94%.
After Benny, Carl has to roll a sum of 10. There are 27 ways to roll a sum of 10. So, 27/216 = 12.50%
All of the other possibilities will mean that Darra will win. So, (216 - 27 - 21 - 15) / 216 = 70.83%
Lucky Darra!