A type of chocolate bar does contain a prize voucher with probability p, 0 ≤ p ≤ 1. Whether or not a bar does contain a prize voucher is independent of other bars. A hungry student buys 8 chocolate bars. Let X denote the number of bars without prize vouchers that she finds and its probability mass function (pmf)
is given below:

A third student keeps buying chocolate bars until he finds 5 prize vouchers. Let W be the numbers of bars
before getting the 5 prize vouchers.
(i) Write down the pmf of W.
(ii) Calculate Pr(W = 2).

3 4 6. 8 X:x 1 Pr(X: x) k4 k3 k2 k, k k k2 k3 k4