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% don’t 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.

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Thank you!