3. Ruby sells cookies for $2.5 per pack, and each of them costs $0.8 to make. All unsold cookies would be sent to charities for free at the end of the day. What is the optimal service level (i.e., critical ratio) of selling the cookies?

A. 24%

B. 68%

C. 76%

D. 32%

4. A restaurant manages the inventory of paper napkins based on a continuous review system with the order quantity Q = 50, and the reorder point = 15. The lead time is 2 days without uncertainty. At the end of day 0, the inventory position = on-hand inventory = 30. The demand in the following five days is 6, 8, 4, 9, and 2, respectively. What is the inventory position at the end of day 5?

A. 36

B. 29

C. 51

D. 24

5. John sells 300 packs of candies per week at $40 per pack. The candies are ordered from a supplier who charges John $60 per order and $20 per pack. John's annual holding cost percentage is 0.2. Assume John operates 50 weeks a year. What is the economic order quantity that minimizes the total ordering and holding cost per year?

A. 474

B. 245

C. 671

D. 387