Question

Now let's suppose that there are three bidders who have independent, private values vi which are either 1 or 3. for each bidder, the probabilities of 1 and 3 are both 1/2. what is the seller's expected revenue in this case?

Answer 1

Expected value, 
E[X] = $\sum p_i*x_i$ = (1/2)*1 + (1/2)*3 = 0.5+1.5 = 2