Problem 1 (25 points) 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. Ann Bob Bob Kate Jim 2 20 (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