Donguri Ltd. has a machine costing $860,000 with the estimated useful life of 8 years and an estimated residual value of $60,000. Donguri uses the straight-line method to depreciate its capital assets. The ledger shows a balance of $425,000 in the accumulated depreciation on December 31, 2020. The following transactions are related to the machine:

2021:

February 1 Donguri paid $9,500 to repair a broken part in the machine.

March 31 Donguri paid $70,000 to replace the motor, as a result, the useful life of the machine has been extended for 2.5 more years.

2022:

June 30 Donguri sold the machine for $350,000.

Required:

1. What is the age of the machine on December 31, 2020? Identify the type of expenditure for the transaction on February 1 and March 31, 2021. (5 marks)
2. What is the annual depreciation expense amount before the estimate changes? What is the annual depreciation expense amount after the estimate changes? (5 marks)
3. Please record all journal entries for 2021. (6 marks)
4. Please calculate the gain or loss on the disposal of the machine, and record all journal entries related to the disposal of the machine. (8 marks)