4. A store sells a special item whose daily demand can described by the following pdf:

The store is comparing two ordering policies: (1) Order up to 3 units every 3 days if the stock level is less than 2, else do not order. (2) Order 3 units every 3 days if the stock level is zero, else do not order. The fixed ordering cost per shipment is $300 and the cost of holding excess units per unit per day is $3. Immediate delivery is expected.

(a) Which policy should the store adopt to minimize the total expected daily cost of ordering and holding?

(b) For the two policies, compare the average number of days between successive inventory depletions.