Two gamblers, Billy and Edward, play the following game: Billy repeatedly tosses
a fair coin. After each toss that comes up H, Edward pays Billy one dollar. After
each toss that comes up T, Billy pays Edward one dollar. The game continues until
either one or the other gambler runs out of money. If Billy starts with $A and
Edward starts with $B:
i. Find the model for the wealth process of player Billy, Un. [2 Marks]
ii. Show that Un is a martingale. [4 Marks]
iii. Find the probability that Billy loses all the money to Edward .