please solve carefully

Illustration 3: From the following balances calculate cash from operations: December 31 2010 2011 Profit and loss a/c balance 75,000 1,55,000 Debtors 45,000 42,000 Creditors 20,000 26,000 Bills receivable 12,000 15,000 Cash in hand 2,500 3,000 Prepaid expenses 1,600 1,400 Bills payable 18,000 16,000 Cash at bank 8,000 10,000 Outstanding expenses 1,200 1,600 Income received in advance 250 300 Outstanding income 800 900 Additional Information: (i) depreciation written off during the year rs. 10,000 (ii) transfer to general reserve rs.10,000