HOW MUCH TIME EY GDS TAKE TO RELEASE OFFER LETTER?

I have interview given interview on last week Thursday after that 1 hour later received mail from HR to submit document ( like pay slip, degree, offer in hand ) after that next week monday hr call and discuss about salary and told u will get offer within 5 business days. After that Tuesday one application automatically applied with status as "background verification investigation in progress". How much time it takes to release offer letter ?