(SAC evaluation question) A bag contains four numbered pieces of paper using numbers 1, 2, 3, and 4. Let Y be the number on a randomly selected piece of paper.
a. Find the probability distribution (mass) function p(y) = P(Y = y) for y = 1, 2, 3, and 4.
y 1 2 3 4
p(y)
b. Find E(Y). [Hint: the answer is 2.5, please show details]