For a discrete random variable XXX with PMF P(X=k)=k10P(X=k) = \frac{k}{10}P(X=k)=10k for k∈{1,2,3,4}k \in \{1, 2, 3, 4\}k∈{1,2,3,4}, is this a valid PMF?
Yes, because the sum of probabilities is 1.
No, because the probabilities are not equal.
No, because the sum of probabilities is not 1.
Yes, because P(X=k)≥0P(X=k) \geq 0P(X=k)≥0 for all kkk.