Suppose there are three bills in a wallet. One of thebills is a $1, one is a $5, and one is a $10 bill. You selecttwo bills at random without replacement from the wallet, and notethe value of the bills selected. The sample space S consistsof the three equally likely outcomes {($1, $5), ($1, $10), ($5,$10)}. Let X be the total of the two bills selected.
a) What is the mean? (Note: The answer key says $4, but it doesn't make any sense to me)
b) What is the probability that X is at least 4? (Note: The answer key says 2/3 but again, it doesn't make any sense)