The probability of winning is .5, the probability of losing is .5, and the payoff (because this is even money) is 1 -- for every $1 you bet, you make or lose $1. Thus, the formula is (1*.5-.5)/1 ...

According to the balance sheet for the same time period, Wal-Mart had $80.55 billion in stockholders' equity and $44 billion in long-term debt, for a total invested capital of $124.55 billion.

Now we can use the joint probability formula noted above to figure out what the joint probability is for this event by multiplying each individual event together. 1/6 x 1/6 = 1/36 ...