A's old share= 2/5
B's old share= 2/5
C's old share= 1/5
D is admitted for 1/6th share. C will retain his original share.
Hence, remaining share= 1- [1/6] - [1/5]
= 19/30
This remaining share will be shared by A and B in their old ratio, i.e, 2:2
A's new share= 2/4 * 19/30
= 38/120
B's new share= 2/4 * 19/30
= 38/120
New Profit sharing ratio= 38:38:24:20
= 19:19:12:10
Sacrificing ratio= old ratio- new ratio
A's sacrifice= 2/5- 19/60
= 5/60
B's sacrifice= 2/5- 19/60
= 5/60
Sacrificing ratio= 5:5= 1:1
[Note: since nothing is mentioned, we assume that only A and B have sacrificed since C retains his old share]