X = number of jobs held during the past year for work study students at a university is as follows: 0, 1, 2, 3, 4, 5 f(x):12, a , 0.28, 0.18, 0.06,...

X = number of jobs held during the past year for work study students at a university is as follows:

X: 0, 1, 2, 3, 4, 5

f(x): 0.12, a, 0.28, 0.18, 0.06, 0.02

Find a. Find the probability that a randomly selected student held 3 or more jobs during the past year. Find the cumulative distribution form. Find the E(X). How many jobs would you expect a randomly selected student to hold in the past year?