Consider selecting at random a student who is among the 15,000 registered for the current semester at a school.

Let X be the number of courses for which the selected student is registered and suppose that X has probability distribution

x: 1 2 3 4 5 6

P(x): 0.01 0.03 0.13 0.25 0.39 0.19

1. Find the cdf of X.
2. Find the expected number of courses taken by a student in this semester.
3. Find the standard deviation of X.
4. Find the median of this distribution.