@priyas614, you can probably write a letter explaining why you need to apply for a BOWP including,
1. Details about PR application - with AOR, paste a copy of your AOR letter.
2. Current work permit number and the date of expiration.
It varies from one application to another. My wife and I applied for BOWP on 23 Feb, and got the approval yesterday.
That makes it 17 days. And please note, you don't always get notified by email. Check myCIC often :)