Develop a general formula for depreciation defining what each variable in the formula stands for.
$\displaystyle A_t = A_0(1-k)^t$
$\displaystyle A_t$ = Value at time t
$\displaystyle A_0$ = Initial value (at t=0)
$\displaystyle k$ = A positive constant measuring the drop
$\displaystyle t$ = time since t=0