Computing Depreciation Expense for Change in Useful Life

Phelps Company purchases equipment on January $1$ of Year $1,$ for $$36,000$ which will be depreciated using the sum$-$of$-$years$-$digits method. The equipment has a residual value of $$6,000$ and a useful life of three years. On January $1$ of Year $2,$ Phelps decides that the machine has an original total useful life of four years $($instead of three years$)$ and $$3,000$ residual value. What is depreciation expense for Year $2?$

Depreciation expense for Year $2$:

NOTE this is not a change in method to straight line. It is just a change in estimate while keeping sum of years!!!