Explanation:

- Calculation of firm's total capital after Z's admission:

- X's capital: Rs1,80,000

- Y's capital: Rs2,00,000

- Z's capital: Rs3,40,000

- Total: Rs7,20,000

- Evaluating Z's Share:

- Z is entitled to 1/3rd of the firm’s total capital.

- 1/3rd of Rs7,20,000 is Rs2,40,000.

- Z brings in Rs3,40,000 indicating he paid extra Rs1,00,000 as goodwill.

- Goodwill Calculation:

- Goodwill = Total capital brought by Z - His share of capital

- Goodwill = Rs3,40,000 (Z's capital) - Rs2,40,000 (1/3rd of total capital)

- Goodwill of A = Rs1,00,000

Goodwill of firm = 1,00,000 x 3/1 = 3,00,000