A random variable X can assume six values: 0, 1, 2, 3, 4, 5. A portion of the probability distribution is shown here:

X 0 1 2 3 4 5

p(X) 0.15 0.1 0.05 0.3 ? 0.2

(a) Find P(X = 4). (b) Calculate the population mean, variance, and standard deviation. (c) What is the probability that x is greater than 2; (d) What is the probability that x is less than 2; (e) What is the probability that x is greater than or equal to 2; (f) What is the probability that x is less than or equal to 2; (g) What is the probability that x is less than 4 and greater than 1; (h) What is the probability that x is less than 4 or greater than 1;