$4.$ A gas$-$powered electric generator is purchased by a public utility as part of an expansion program. It is expected to be useful, with proper maintenance, for an estimated $30$ years. The cost is $$16\mathrm{.}5$ million, installed. The salvage value at the end of $30$ years is expected to be $10\mathrm{.}0\%$ of the original cost.

a$.$ What is the MACRS$-$GDS property class?

b$.$ Determine the depreciation deduction $($dt$)$ and the unrecovered investment $($Bt$)$ for years $1,5,$ and the last depreciable year of the generator.

D$1=$ $ $\_\_\_\_\_\_\_\_\_\_,$ B$1=$ $ $\_\_\_\_\_\_\_\_\_\_$

D$5=$ $ $\_\_\_\_\_\_\_\_\_\_\_\_,$ B$5=$ $ $\_\_\_\_\_\_\_\_\_\_$

Dlast year $=$ $ $\_\_\_\_\_\_\_\_\_,$ Blast year $=$ $ $\_\_\_\_\_\_\_\_\_$