Suppose that, starting with a fortune of f₀ units, you bet a units each time on evens at roulette (so that you have a probability of 18/37 of winning at Monte Carlo or 18/38 at Las Vegas) and keep a record of your fortune f_n and the difference d_n between the number of times you win and the number of times you lose in n games. Which of the following are stopping rules?

(a) The last time n at which f_n ≥ f₀. 

(b) The first time that you win in three successive games. 

(c) The value of n for which f_n = max {0≤k<∞} f_k.