When you send a text on a phone the software sends a 'setup' message to the local base station. If there is no response, another setup message is sent and this is repeated up to n = 6 times. If after 6 attempts there is no response, the transmissions end and the phone indicates this with a 'busy' signal. Suppose all transmissions are independent and are acknowledged with probability p. (A) Sketch a tree diagram to illustrate the setup procedure. (B) Write down and justify the PMF for the random variable K, the number of setup attempts in a call. (C) What is the probability that the phone will give the busy signal. (D) If p = 0.5 what is the minimum value of n that the phone manufacturer must set to ensure that the probability of a busy signal be less than 0.01