The restaurant is thinking of hiring more personnel to cut down the service time. However, the additional cost of increasing personnel is estimated to be $0.50 per customer. The results of sampling with the added personnel yields the following waiting times (in minutes): 8.4, 5.6, 7.8, 6.8, 8.5, 6.2, 6.5, 5.9, 6.4, 7.5. Is it cost-effective to add personnel? What is the total expected monthly loss?