$A$ and $B$ are partners in a firm sharing profits in the ratio of $5:3$. They admit $C$ as a new partner for $\frac{1}{7}$ th share in the profits. The new profit sharing ratio will be $4:2:1$. The sacrificing ratio of $A$ and $B$ is

1. A
   5:3
2. B
   4:3
3. C
   3:5
4. D
   2:5