mine took about 7 weeks to get the offer after the final interview. So basically if they are interested in you, they will let you know after the interview, probably a day or two. Then they will start to process your application - mainly is security clearance. My clearance took about 6 weeks. The following week inform of the offer.

you can get in touch with HR 1 or 2 weeks later after your interview to check your status. whether any 2nd interview or they already processed your application.

I think to get the whole contract sign probably 8-9 weeks after they processed your application.