Double$-$declining$-$balance depreciation

A building acquired at the beginning of the year at a cost of $$88,400$ has an estimated residual value of $$5,300$ and an estimated useful life of four years. Determine following.

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

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