Read the following passage:

Four colleagues A,B,C and D during lunch time which is from 1:00 - 1:30 pm on a given day go for a walkthrough 2 different routes i.e. they exit from one gate and enter from the other one. A straight path, withinthe office, connects Gates 1 and 2. A and B exit from Gate 1 and enter from Gate 2, and again movetowards Gate 1 using the straight path; while C and D exit from Gate 2 and enter from Gate 1, and againmove towards Gate 2 using the straight path. The routes are in clockwise direction i.e. Gate1 to Gate 2 aperson can only walk in clockwise direction and similarly from Gate 2 to Gate 1. It takes 4 minutes to walkfrom Gate 1 exit to Gate 2 entrance and 6 minutes to walk from Gate 2 exit to Gate 1 entrance. The timetaken to walk from Gate 1 to Gate 2 and vice versa within the office is 1 minute. Initially, the colleaguesleave at a gap of 2 minutes each in the order of B, A, C and D during lunch time. Each person starts thenext round of walk immediately after completing the first round.