Double$-$declining$-$balance depreciation

A building acquired at the beginning of the year at a cost of $$112,800$ has an estimated residual value of $$3,400$ and an estimated useful life of $4$ years. Determine the following.

$($a$)$ The double$-$declining$-$balance rate $\%$

$($b$)$ The double$-$declining$-$balance depreciation for the first year $