awk command of add column to sum of repeated column

Question

i have a data set tab separated like this:

A  B  C  D
1  aaa 1 2
1  aaa 3 4
1  aaa 5 6
1  bbb 7 8
1  ccc 9 1
1  ccc 2 3
1  ffffd 4 5
1  ffffd 6 7
1  ffffd 8 9
1  ffffd 1