b. Firebase rules provides a way to identify user role while performing read and write operations. These rules will acts a security layer on the server before perform any CRUD operation. By default the rules allows user to perform read & write operation only after authentication. The below rules allow authenticated users only to read or write data. { "rules" : { ".read": "auth != null", ".write": "auth != null" } } Write a rules to validate the username to be less than 50 chars, mobile number and email to be valid using email regular expression