Question 4 20 pts 4.a (20 points} Consider a protocol that works much like the selective repeat protocol (SRP) discussed in Set 8 of the class notes, but with more protection in retransmissions. The protocol is such that the original packet transmission succeeds with probability p and any retransmission of a packet succeeds with probability r > ,0, because of added coding protection used in retransmissions. As a result, the sender spends one transmission for the first transmission of a packet and with probability pthe receiver gets it. With probability 1 pthe sender spends one transmission and goes to the retransmit state. In that state, the sender spends one transmission for each retransmission of the packet and with probability rthe receiver gets it. Otherwise. with probability 1 rthe sender goes back to the same retransmit state and tries again subject to the same probabilities. Let Xbe the random variable denoting the number of transmissions (original and retransmissions) needed to receive a packet correctly at the receiver. Compute EX} when p = 0.2 and g: 0.8. Use the method we covered related to the law of total probability