Suppose that I give a four-point multiple-choice exam and have figured out that the resulting score X has the following probability mass function a.

Suppose that I give a four-point multiple-choice exam and have figured out that the resulting score X has the following probability mass function 

a.  Plot the cumulative distribution function (CDF) of x, Fx(X).

b.  Find E[X], the expected value of X

c. Find Var(X). 

d. What is the probability that a student gets a score greater than or equal to 3 given that her score is greater than 1,