A database for an online bookstore needs to store information about books $($identified by isbn,

with title and price as attributes$),$ authors $($identified by author$\_$id$,$ with name and url as

attributes$)$ and publisher $($identified by publisher$\_$name, with address and url as attributes$).$

Each book is written by one or more authors and published by exactly one publisher.

$($a$)$ Draw an E$-$R diagram that captures all of the information provided above.

$($b$)$ Define tables using SQL that correspond to the above E$-$R diagram. You must define

the smallest number of tables all in BCNF $($no proof required$).$ For each table, specify

primary and foreign keys as well as necessary constraints.