Starbucks coffee is considering opening a drive-through window. Management estimates that customers will arrive at a rate of 12 per hour, the employee staffing the window can serve customers at a rate of one every Four (4) minutes. Assume Poisson arrival and exponential service. 1. What is the service rate? 2. what is the average time between arrivals (time between 2 arrivals)? 3. What percentage of Ume the employee is idle (free)