Consider a database schema with three relations:

Books$($bid:integer, bname:string, author:string, pubyear:integer, pubcompany:string$)$

Students$($sid:integer,sname:string, age:real, state:string$)$

Reads$($sid:integer,bid:integer,year:integer$)$

$($The primary keys are underlined in each relation. A book is uniquely identified by bid. A

student is uniquely identified by sid. If a student reads a book, a record will be present in the

Reads relation, with that sid and bid and the year the book was read.$)$

and the following relations instances: