probability - 6 sided die probabilities

i am currently working on a study guide and one of the questions i am completely stuck on and have no idea how to do it.
Question is.
You are interested in the number of rolls of a fair $6$ sided die until a number $2$
shows up.

Let $X =$ The number of times you roll the die until a number $2$ shows up.

(a) What type of random variable is $X$?

(b) How many rolls do you expect it to take? That is, what is the expected value, or mean, of the random variable $X$?

(c) What is the probability you roll a $2$ for the first time on the fourth roll? i.e. What is $P(X = 4)$?