You have probably noticed that the Stillwater students chose to include a time stamp field as part of the primary key for all of the relations except...

You have probably noticed that the Stillwater students chose to include a time stamp field as part of the primary key for all of the relations except PRODUCT. Explain why you think they decided to include this field in each relation and why it is part of the primary key. Are there other alternatives to a time stamp field for creating primary key of these relations?