There are two envelopes, each of which has a check for a unif(0,1) amount of money, measured in thousands of dollars. the amounts in the two envelopes are independent. you get to choose an envelope and open it, and then you can either keep that amount or switch to the other envelope and get whatever amount is in that envelope.
suppose that you use the following strategy: choose an envelope and open it. if you observe 'u', then stick with that envelope with probability 'u', and switch to the other envelope with probability 1-u
a) find the probability that you get the larger of the two amounts
b) find the expected value of what you will receive