Explanation:

- In this scenario, P is responsible for all realisation expenses.

- He is set to receive Rs2,000 for covering these costs.

- P actually incurred expenses of Rs2,500.

- Generally, the realisation account is debited with the agreed amount to be paid to the partner for realisation expenses, which is Rs2,000 in this case.

- P's actual spending does not alter the amount debited since the contract specifies a Rs2,000 payment to P.

- Option 4: Rs2,000 is correct.

- Option 1 (Rs500) is incorrect because Rs500 is the excess amount P had to pay, not the debit amount.

- Option 2 (Rs2,500) is incorrect as it represents P's actual expenses, not the agreed payment.

- Option 3 (Rs4,500) is incorrect; this sum combines payment and expenses but isn't the correct accounting entry.