An ophthalmologist's office operates 52 weeks per year, 6 days a week. It purchases disposable contact lenses for $11.70 per pair and sells for $50. Demand is 90 pairs per week. Order cost is $54 per order. Annual interest rate is 27%. Lead-time is 3 weeks. Standard deviation of weekly demand is 15 pairs. Given that 98% service-level. Assume demand is normally distributed.

1. Find a reorder point - Order quantity (Q, s) policy for this situation
2. Find average order frequency of the policy (a)
3. Clearly identify different types of stocks: cycle, safety and pipeline
4. Assume that lead time is probabilistic, normally distributed with mean 3 weeks and variance 0.2 weeks, determine the reorder point - Order quantity (Q,s) policy.

(Supplement definition: Cycle stock: average inventory on hand, at any point. Safety stock: inventory kept on hand to allow demand uncertainty. Pipeline stock: goods in transit between levels of the multi-echelon distribution system or between adjacent workstations in factory (mean demand during lead time)