Companies, identified by Company ID and described

by Company Name and Industry Type, hire consultants,

identified by Consultant ID and described by

Consultant Name and Consultant Specialty, which is

multivalued. Assume that a consultant can work for

only one company at a time, and we need to track only

current consulting engagements. Draw an ERD for this

situation. Now, consider a new attribute, Hourly Rate,

which is the rate a consultant charges a company for

each hour of his or her services. Redraw the ERD to

include this new attribute. Now, consider that each time

a consultant works for a company, a contract is written

describing the terms for this consulting engagement.

Contract is identified by a composite identifier of Company

ID$,$ Consultant ID$,$ and Contract Date. Assuming

that a consultant can still work for only one company

at a time, redraw the ERD for this new situation. Did

you move any attributes to different entity types in this

latest situation? As a final situation, now consider that

although a consultant can work for only one company

at a time, we now need to keep the complete history

of all consulting engagements for each consultant and

company. Draw an ERD for this final situation. Explain

why these different changes to the situation led to different

data models, if they did.