hi all and especially mr_fantastic! remember the post "what is the...". that one was the case of Bayesian theorem. now what about this one?

Consider two players *A* and *B* who are accompanying in a sequence of independent games. Probability of **A** win is *p^2*, probability of *B* win is *q^2*, and probability of equality (neither *A* nor *B* wins) is *2pq* (*p+q=1* and *0<p<1*). At each run, the winner gets *2* points and in the situation of equality each player gets *1* point. Suppose *X* and *Y* are the total points of relatively *A* and *B* after the end of *n* runs of game. What is *COV(X, Y)*?

ps. power is denoted by ^.

{hence my absolute unfamiliarity with posting rules!!}