For the function $f(x)=x^3+3x^2-9x$ find:

$(a)$: The open intervals where $f(x)is$ increasin$\frac{g}{d}$ecreasing,

$(b)$: The open intervals where $f(x)is$ concave $u\frac{p}{d}$own,

$(c)$: The local maximums and minimums $off(x)$

$(d)$: The $absolute$ minimum and maximum $off(x)on0,2.$