As per last year's experience, you shld be notified (via phone) 4 weeks after the first interview if there is a 2nd interview. Else you shld be getting a letter of rejection within 4 weeks.
My daughter was accepted within 1 week after 2nd interview too. You should reply accepting the offer or not in a short period, says, in 2 weeks?! I can't remember exactly. As SMC was our first choice, we paid at once.