In a smoking survey among boys between the ages of 12 and 17, 78% prefer to date
nonsmokers. 1% prefer to date smokers, and 21% donít care. Suppose seven such boys are
selected randomly and X equals the number who prefer to date nonsmokers and Y equals the
number who prefer to date smokers.
(a) Determine the joint p.m.f. of X and Y. Be sure to include the support of the p.m.f.
(b) Find the marginal p.m.f. of X. Again, include the support.