$L$ and $M$ are partners sharing profits in the ratio $3:2$. $N$ is admitted as a partner for $\frac{1}{5}\text{th}$ of the share which is acquired entirely from $L$. Goodwill of the firm is valued at Rs. $40,000$ on $N$ 's admission. $N$ will have to pay for Goodwill:

First, find $N$ 's share of goodwill:
$$\text{Total Goodwill of the Firm}=\text{Rs. }40,000$$
$$N\text{’s share of profit}=\frac{1}{5}$$
$$\text{Goodwill premium brought by }N=40,000\times \frac{1}{5}=\text{Rs. }8,000$$
Premium for goodwill brought by a incoming partner is distributed exclusively among the existing partners in their sacrificing ratio.Since $N$ acquired his complete share entirely from $L$, partner $L$ is the sole sacrificing partner, while partner $M$ 's sacrifice is zero.Therefore, the entire premium of Rs. 8,000 must be credited exclusively to $L$.