The Kitchener Furniture store gets an average of 50 customers per shift. Marilyn Helms, the manager, wants to calculate whether she should hire one, two, three, or four salespeople. She has determined that average waiting times will be seven minutes with one salesperson, four minutes with two salespeople, three minutes with three salespeople, and two minutes with four salespeople. She has estimated the cost per minute that customers wait at $1. The cost per salesperson per shift (including fringe benefits) is $70. How many salespeople should be hired?