Attempt No.1

1. 72, 24, 48
2. 1
3. 11, D
4. Bill can Bid $99 on other sprinters such as C,D,E for a sure win.
But to increase the chance, he will probably bet on Sprinter B. And, at most he can afford to bet $41.8333. Not a single penny more. In this way even if he loses by chance in the bet, he will still win the $1,000,000. In this case, the winning chance for him is 92.3%.