Problem 4 (18 points). Demand for a product is normal; 25 units per week in average with a standard deviation of 8 units per week. Every unit cost $22 and require an average of 4 weeks to obtain from the vendor, this lead time has a standard deviation of 1 week. The cost of place an order is $35, and the inventory holding cost is $3.00 per unit per year. No stockouts are allowed because there is a cost of $1,000 /stockout. The company works 50 weeks per year. a. (5 points). What is the economic order quantity? b. (13 points). What is the optimal reorder point and the safety stock at a service level of 90%