Amount paid per month = ₹ 4,000
Total amount paid in an year
= 12 × 400 = ₹ 48, 000
Total interest paid to the bank
= ₹ 8,000
Interest = Total Amount paid back - Total loan amount
₹ 8,000 = ₹ 48,000 - Total loan amount
Total loan amount = ₹ 48,000 - ₹ 8,000 = ₹ 40,000