50. Three tables listed below show random variables and their probabilities. However, only one of these is actually a probability distribution. x P(x) x P(x) x P(x) 25 0.1 25 −0.6 25 0.5 50 0.7 50 0.2 50 0.3 75 0.2 75 0.1 75 0.1 100 0.4 100 0.1 100 0.1

a. Which of the above tables is a probability distribution?

b. Using the correct probability distribution, find the probability that x is: 1. Exactly 75. 2. No more than 50. 3. More than 25.

c. Compute the mean, variance, and standard deviation of this distribution.