It minimizes average flowtime, but not the average number of jobs in the system. It may be unsuitable when customers are present in the job queue. It generates worse average lateness than use of Slack Time Remaining. Long processing time jobs may tend to stay in the system. Both b and d are true.
Setup reduction leads, ultimately, to decreased production lead time.
Setups are reduced as a result of reducing lot sizes. When inventories are reduced, the use of tools such as preventive maintenance and SPC must be increased. The benefits of small-lot production can be realized in a push mode of production.