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. let x equal the number who prefer to date nonsmokers and y equal the number who prefer to date smokers. (a) determine the joint pmf of x and y. be sure to include the support of the pmf. (b) find the marginal pmf of x. again include the support.