Explanation:

- The total balance sheet of the firm is Rs 77,000.

- The assets side includes:

- Preliminary expenses: Rs 2,000

- Profit & Loss Account (Debit) Balance: Rs 4,000

- Cash Balance: Rs 1,800

- Preliminary expenses and the debit balance of Profit & Loss Account are fictitious assets and do not yield cash upon realization.

- Hence, actual assets (excluding preliminary expenses and debit balance) are Rs 77,000 - (Rs 2,000 + Rs 4,000) = Rs 71,000.

- Cash balance: Rs 1,800 (already in liquid form)

- Loss on realization: Rs 6,300

- Total realisable value of assets = Rs 71,000 - Rs 6,300 = Rs 64,700

Option:3, Rs 64,700 is correct.