6 I. L. Pea is a well-known mail-order company. During the Christmas rush (from November 1 to December 15), the number of orders that I. L. Pea must fill each day (five days per week) is normally distributed, with a mean of 2,000 and a standard deviation of 500. I. L. Pea must determine how many employees should be working during the Christmas rush. Each employee works five days a week, eight hours a day, can process 50 orders per day, and is paid $10 per hour.

If the full-time work force cannot handle the day’s orders during regular hours, some employees will have to work overtime. Each employee is paid $15 per hour for overtime work. For example, if 300 orders are received in a day and there are four employees, then 300 - 4(50) =100 orders must be processed by employees who are working overtime.

Since each employee can fill  50/8= 6.25 orders per hour, I. L. Pea would need to pay workers 100/6.25= 16 hours of overtime for that day. To minimize its expected labor costs, how many full-time employees should I. L. Pea employ during the Christmas rush?