This is a pretty easy problem you can look at A as adding all the cases subtracting the E[x] (where x is the breifcases) and then divided by 4 (due to there only being 4 cases left).
for b all you really have to do is find E[x] and times it by .7 because we know since the taxes is a constant we can evaluate it during the summation or after the summation (and it is easier and faster to do it afterwards).
