My son went in at 4pm and came out at 4:50
Some kids went in later but came out very fast like 15mins. I asked other parents and they said maybe in different groups so some were faster and some were slower.
I also saw a girl from my girl's batch came out after 20 mins (vs my girl 40 mins). I guess after doing part A, the girl had her one on one interview first, earlier than other candidates(30 in the big batch, around 10 in a row). My girl said only a few questions asked. If no wait time I guess part A and B might take only 10 -15 mins.