1. Question 6

The lock box operation at NBD bank involves three stages.Envelopes arrive from the post office every half hour in batches of 30.In the first stage the envelopes are automatically opened at a rate of 60 per hour.In the second stage the contents (deposit slips) are scanned and printed.This optical character recognition machine is capable of processing 60 deposit slips per hour.In the final third stage, deposit confirmation records are inserted into envelopes at a rate of 60 records per hour, to be mailed to customers.Between each stage the contents of envelopes are moved in batches of 30.

A suggested "process improvement" at NBD calls for movement between stages in batches of 15 rather than 30.As a result the cycle time taken to process each batch of 30 envelopes coming from the post office is expected to

Decrease by 15 minutes.

Decrease by 20 minutes.

Decrease by 30 minutes.

Decrease by 10 minutes.

Remain unchanged.