At the moment that a call is sent the software sends a setup message to the call station. If no response is given, another setup message is sent and this process repeats up to 6 times. If following the 6'th attempt no response is given, the transmissions end and the phone shows this with a busy signal. Assume that all of the transmissions are independent and have a probability denoted as the variable x.

1) Write out a tree diagram to depict the procedure of the setup.

2) Write out the process for probability mass function (PMF) for the random variable X, which is the number of the setup attempts in a call.

3) Determine the probability the phone will give out a busy signal.

4) Assume a value of x = 0.5. Determine the minimum value denoted as y that the phone provider will set to make sure that the probability that the signal will come out as busy is smaller than the value of 0.01.