The following are the operation times and due dates for six jobs (each job undergoes a single operation):

Job	Processing Time (days)	Due Date (days hence)
A	5	17
B	6	25
C	10	24
D	3	9
E	7	16
F	4	21

The firm operates seven days per week. Assign the jobs according to each of the following priority rules:

1. shortest operation time (SOT)
2. earliest due date (EDD)
3. slack time remaining (STR)
4. critical ratio (CR)

If a priority rule results in a tie between two or more jobs, break the tie by scheduling the tied jobs in alphabetical order.

Evaluate each of the above priority rules with the objective of minimizing the mean tardiness. The term tardiness is used here, rather than lateness, to indicate that there is no credit for a job completed early. A job completed early simply has a tardiness value of 0. In other words, lateness and tardiness are the same if the job is completed after the due date, but different if the job is completed before the due date. For minimizing mean tardiness, no rule is best under all circumstances. Which one of the priority rules did you determine to be best in this particular case?