A drug store is trying to decide the optimal number of check-out counters to staff on a daily basis. The store uses a multi-server system. It is observed that on average 45 customers will arrive per hour, and on average it takes 3 mins to serve one customer. Your goal is to minimize the total cost of service. The average hourly cost of waiting for each customer is estimated to be $70/hour, and the staff hourly wage is $12/hour. How many check-out counters should be staffed if the goal is to minimize the total cost of service? What is the minimum total cost?