The time taken to change the four tires of SUVs at BANZ Garage is assumed to be normally distributed with a mean of 45.75 minutes and a standard deviation of 6.5 minutes. If two SUVs serviced by 2 different tiremen are randomly selected, find the probability that the first tireman changed the tires in at most 46.5 minutes, while the second took at least 4 minutes longer than his colleague to complete the job.