What is the formula for calculating double$-$declining$-$balance depreciation?

Multiple choice question.

$($Cost $$ Residual value$)$ x $(1/$useful life$)$

$($Cost $$ Residual value$)$ x $($actual production this period$/$estimated total production$)$

$($Cost $$ Accumulated depreciation$)/(2$ x useful life$)$

$($Cost $$ Accumulated depreciation$)$ x $(2/$useful life$)$