After the accountant of Strikers Ltd had prepared the financial statements for the year ended 30 June 2020, the following errors came to light:

1. A motor van purchased at a cost of $12,000, with accumulated depreciation at the beginning of the year of $4,000, had been depreciated at 20% using the reducing-balance method rather than the straight-line method of depreciation.
2. The payment of $1,500 for a trade payable had been treated as a cash purchase.
3. Withdrawals by the owner of $3,000 during the year had been treated as part of the salaries and wages expense.
4. Bank charges of $400 during the year had been treated as interest charges.

Required:

What is the effect on profit of each of these errors?