You just landed a job as the human resource manager for the Cookeville Regional Medical Center’s Emergency room! Past research demonstrates that the number of patients arriving through the ER on...

You just landed a job as the human resource manager for the Cookeville Regional Medical Center’s Emergency room!  Past research demonstrates that the number of patients arriving through the ER on Friday night between 11pm and midnight follows a Poisson distribution with a mean number of 4.0 patients.  Calculate the probability that at least 1 patient will arrive during this time.  This information will help the Human Resources Director staff the ER with the optimal number of doctors and nurses.