The `XI^(th)` class students of ALLEN designed a rocket. The rocket was launched from cycle stand of ALLEN straight up into the air. At `t = 0`, the rocket is at `y = 0` with `V_(y) (t = 0) = 0`. The velocity of the rocket is given by: `V_(y) = (24t - 3t^(2))m//s` for `0 le t le t_(b)` where `t_(b)` is the time at which fuel burns out. vertically upward direction is taken as positive. `(g = 10m//s^(2))`
The expression for the acceleration `a_(y)(t)` valid at all times in the interval `0 lt t lt t_(b)` is

Options

A. `12 t^(2) - t^(3)`
B. `24 -6t`
C. `24t - 6t^(2)`
D. `24 -= 6t - g`