An AS/RS is to be designed for the storage of 60  48 unit loads. The S/R machine will travel horizontally at a speed of 500 fpm; simultaneously, it will travel vertically at a speed of 80 fpm. The storage aisle will be 400 long and 60 tall. The pick-up and deposit station will be located at the end of the aisle and will be elevated 20 above floor level. Assume randomized storage will be used and the storage region served by the S/R is a continuous, rectangular region 400  60. The P/D time will be 0.30 minute.

a. Determine the single-command cycle time, including P/D times.

b. Determine the dual-command cycle time, including P/D times.

c. Suppose three classes of products are to be stored in the storage aisle. Fast movers will be stored in a rectangular region defined by the following coordinates: (0, 0),

(0, 40), (125, 40), and (125, 0). Medium movers will be stored in an L-shaped region between the fast and slow movers. Slow movers will be stored in a rectangular region defined by (250, 0), (250, 60), (400, 60), and (400, 0). Fast movers represent 60% of the storage and retrieval operations performed; medium movers account for 30% of the activity; slow movers represent the balance. Determine the average single-command cycle time, including P/D times.