The correct answer is A.
A and B share the profit in the ratio of 4 : 3. This means that A gets 4 parts of the profit and B gets 3 parts of the profit. The total number of parts is 4 + 3 = 7.
C is admitted to the partnership for 1/5 of the profit. This means that C gets 1 part of the profit. The total number of parts is now 7 + 1 = 8.
A and B agree to bear 3/20 and 1/20 of the 1/5 profit, respectively. This means that A gets 3/20 of 1/5 = 3/100 of the profit and B gets 1/20 of 1/5 = 1/100 of the profit.
The new profit sharing ratio of A, B and C is 4/7 : 3/7 : 1/8 = 15 : 13 : 7.
Option B is incorrect because it does not take into account the fact that A and B agree to bear 3/20 and 1/20 of the 1/5 profit, respectively.
Option C is incorrect because it does not take into account the fact that the total number of parts is now 8.
Option D is incorrect because it does not take into account the fact that A and B share the profit in the ratio of 4 : 3.