1.5.4. Let pX(x) be the pmf of a random variable X. Find the cdf F(x) of X and sketch its graph along with that of pX(x) if:
(a) pX(x) = 1, x = 0, zero elsewhere.
(b) pX(x) = 1/3, x = -1, 0, 1, zero elsewhere.
(c) pX(x) = x/15, x = 1, 2, 3, 4, 5, zero elsewhere.