The winning team has the lowest time, 2nd place the second lowest time and so on.
From the times you provided, F is the shortest at 2:47.874, giving them first place.
Second place goes to team A on 2:48.018
Third place is D=2:48.099
So, to recap, 1st=F,2nd=A,3rd=D
To find the difference in times between 1st and 2nd, simply subtract the 1st place time from 2nd place.
2:48.018-2:47.874=1.44
So, to answer the second part of the question, the difference between A and B is 1.44 minutes