I tried using the formula:

$\displaystyle cov[V,W] = E[VW] - E[V]E[W]$

I assumed this takes on a binomial distribution with

$\displaystyle E[X] = np$

Hence for E[V] and E[W] I obtained 0.55n and 0.45n respectively. After this I am stuck on this question.

Any hints would be greatly appreciated!

Linda