Suppose N1 is a discrete random variable equally likely to take on any integer in the set the random variable N2 is equally likely to take on any integer in the set , the random variable N3 is equally likely to take on any integer in the set
(a) Find the two-dimensional joint PMF
(b) Find the three-dimensional joint PDF
(c) Find the marginal PDF
(d) What are the chances that none of the three random variables are equal to 1?