Suppose there are three bills in a wallet. One of the bills is a $1 bill, one is a $5 bill, and the third is a $10 bill. You select two bills at random without replacement from the wallet, and note the value of the bills selected. The sample space S consists of the three equally likely outcomes {($1. $5), ($1, $10), ($5, $10)}. Let X be the total of the two bills selected. What is the probability that X is at least $10?