Consider a deck consisting of seven cards, marked 1, 2, 7. three of these cards are selected at random. define an rv w by w ¼ the sum of the resulting numbers, and compute the pmf of w. then compute e(w) and var(w). [hint: consider outcomes as unordered, so that (1, 3, 7) and (3, 1, 7) are not different outcomes. then there are 35 outcomes, and they can be listed.] (this type of rv actually arises in connection with wilcoxon’s rank-sum test, in which there is an x sample and a y sample and w is the sum of the ranks of the x’s in the combined sample.)