Could you please help mee!!! It is really urgent!! PLEASE!!!

The corporation has one plant asset. The asset's original cost was $1,086,500. There is a $51,500 expected residual value and the estimated useful life is 30 years. On January 1 of the current year, following 20 full years of depreciation, the company determined that the asset will be useful for only another 5 years and reduced the expected residual value to $26,500. The change in estimate is needed to reflect advanced technology used in newer equipment currently available on the market. Briggs uses the straight-line method of depreciation.

1. Determine the original, annual depreciation expense recorded for this asset.
2. Compute the net book value of the asset on the date of the change in estimate.
3. Compute the revised depreciation expense after the change in estimate.
4. What is the effect of the change on pretax earnings after the change is implemented? Be sure to indicate if income increases or decreases.