[求助]Question

The plant account of a company is shown below:

plant cost1)1,01,2002 balance $380000;1.04.2002 cash-plant purchases $51000

                (2)1.10.2002 Transfer disposal account-cost of plant sold $30000;31.12.2002 Balance $401000

The company's policy is to charge depreciation on plant at 20% per year on the straight line basis, with proportionate depreciation in years of purchase and sale.

what should the company's plant depreciation charge be for the year ended 31,12,2002?

so, how to do? please write down the detail for me, thank you very much.