The distribution function of is given by

if

if

if

if

if

I have to find

a)

b)

For a) I figured possible values for the random variable were

Doing some subtraction I got:

I am confused. What is b? Is it a possible value that the random variable can take on? Also, is part a) the same thing as saying "find the probability mass function"?

And for part b), I am not sure where to begin with this one. Any help is appreciated.

Thank you very much.

-Jame

(Also I apologize if the table is hard to read, that's the nicest I could get it with tex)