You roll a fair 8-sided die repeatedly until you roll a 7, at which point you stop. Let En be the event that this process stops after exactly n rolls. (a) What is the probability that the process...

You roll a fair 8-sided die repeatedly until you roll a 7, at which point you stop. Let En be the event that this process stops after exactly n rolls.
(a) What is the probability that the process stops after exactly 4 rolls, that is P(E4)?
(b) What is the probability there are at most three rolls?

(c) What is the probability the number of rolls is odd?