A U.S. Postal Service supervisor is looking for ways to reduce stress in the sorting department. With the existing arrangement, stamped letters are machine-canceled and loaded into tubs with

325

letters per tub. The tubs are then pushed to postal clerks, who read and key zip codes into an automated sorting machine at the rate of one tub per

385

seconds. To overcome the stress caused when the stamp canceling machine outpaces the sorting clerks, a pull system is proposed. When the clerks are ready to process another tub of mail, they will pull the tub from the canceling machine area. How many tubs should circulate between the sorting clerks and the canceling machine if

50,000

letters are to be sorted during a

12-hour

shift, the safety stock policy variable,

,

is

0.25,

and the average waiting time plus material handling time is

45

minutes per tub?

The average processing time per tub of letters,

p,

is

nothing

day. (Enter your response rounded to four decimal places.)

The average waiting time per tub of letters,

w,

is

nothing

day. (Enter your response rounded to four decimal places.)

Therefore, the number of tubs that should circulate between the sorting clerks and the canceling machine is

nothing

tubs. (Enter your response rounded up to the next whole number.)