Consider a Schema of relation S S (A:number, B:string, C:string, D:number, E:string) Below also shows you a valid instance of the relation S AB 2 4 Ann Bob Bob Kate Jim 18 20 18 (1a) (10 points) Given a create table statement below for relation S create table s A number, B number unique, C char (3) D number not null, E varchar (1) unique (B, D) Is this a correct or incorrect statement to make the above instance of S valid? List three (3) evidences that support your conclusion (very briefly explain why) Tips: Think about concepts and usages of primary key, unique, not null etc. (1b) (15 points) Consider the same Schema of relation S, now write a create table statement, which would make the instance of the relation S valid For your choice of primary key in your statement (which first of all has to be a candidate key), write just TWO (2) superkeys (not all) for that primary key Tips: Be careful the choice of primary key should not violate the minimal principle