7 On average one in five packets of a breakfast cereal contains a voucher for a discount on the next packet bought. Whether or not a packet contains a voucher is independent of other packets, and can only be determined by opening the packet.

1. State the distribution of the number of packets that need to be opened in order to find one which contains a voucher.
2. Determine the probability that exactly 4 packets have to be opened in order to find one which contains a voucher.
3. Determine the probability that exactly 10 packets have to be opened in order to find two which contain a voucher.
4. I have \(n\) packets, and I open them one by one until I find a voucher or until all the packets are open. Given that the probability that I find a voucher is greater than 0.99 , determine the least possible value of \(n\).