Final answer:
The tardiness is 0 days since the job was completed ahead of schedule.
Step-by-step explanation:
To find the tardiness, you need to consider the difference between the planned duration of the job and the actual duration. If the job was finished 4 days early, it means that the actual duration was shorter than the planned duration. In this case, the tardiness is 0 days since the job was completed ahead of schedule.