Consider the following relational model for NetFlix:

SubscriptionContracts$($ContractID$,$ CustomerID, ServiceAddress, ServiceType, StartDate$)$

Below are the business rules:

Every customer is assigned a unique CustomerID which is the email address that customer uses for registration.

A customer can have multiple subscriptions.

Each subscription is assigned a unique ContractID.

A customer is allowed to have multiple subscriptions for the same ServiceAddress.

A customer is allowed to have only one ServiceAddress.

Each subscription can have one of the two ServiceType: "Rental" or "Periodical".

StartDate is only valid for "Periodical"; in case of "Rental", this field is null. In case of "Periodical", it is the date on which the subscription was purchased.

StartDate is only valid for "Periodical"; in case of "Rental", this field is null. In case of "Periodical", it is the date on which the subscription was purchased.

Now answer following problems:

a$.$ Identify all possible direct $($not transitive$)$ Functional Dependencies in this model. You must answer in the form X$->$Y$.$ You should not mention any Trivial dependencies.

$[2$ Marks$]$

b$.$ Suggest the best possible PK for this table. Justify your selection with explanation. We do not want to decompose the table.

$[1$ Mark$]$

c$.$ Which functional dependencies are redundant? Justify your answer.

$[2$ Marks$]$