It's that time of the year again - Safeway is offering its Monopoly Card promotion. Each time you visit Safeway, you are given one of n different Monopoly Cards with equal probability. You need to collect them all to redeem the grand prize. Let X be the number of visits you have to make before you can redeem the grand prize. Show that var(X)=n (2)-E(X). [Hint: Does this remind you of a particular problem? What is the expectation for this problem?]