x 1 2 3 4 5 P(x) 0.1 0.3 0.1   0.1   A random variable…

x 1 2 3 4 5 P(x) 0.1 0.3 0.1   0.1   A random variable X has the probability distribution shown above. a) What should go in the blank cell to make the distribution valid? b) What is the probability that X is at most 3? c) What is the expected value of X?