In a bank, the wait time to be served is modeled as follows: If X is the wait time (in minutes) model and x is the actual wait time, P(X>x)=[(x 4)exp(-x/4)]/4. Is this a valid model to represent the wait time? If so, what is the probability that the wait time exceeds 8 minutes? What is the probability that the wait time is between 4 and 8 minutes