let X, Y be 2 bernoulli RVs with respective parameters p,q. They are not necessarily independent. Let @ denote P(X=1, Y=1) a) what is the joint PMF f(XY)(x,y)?
b)compute correlation between X and Y
c)Give an example for which the correlation is +1 for some choice of @
d)Give an example of p,q for which correlation cannot be so large as +1 for any choice of @?