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 denotes the number of bars without prize vouchers that she finds and its probability mass function (pmf)
is given below:

A second student keeps buying chocolate bars until he finds a prize voucher. Let Y denote the number of bars he buys before getting a bar with a prize voucher.

If each bar costs 35 takas, what is the expected cost to the second student?

X:x 1 3 4 6 7 8 Pr(X:x) k4 ka k2 k1 k k, k2 k3 k4