If the function f: R → R defined by f(x)=x^3/3-(2 a+3 b) x^2+24 a b x+5 has a local maxima at -4 and a local minima at 4, then a value of 4 a+3 b is

If the function $\displaystyle f: \mathbb{R} \rightarrow \mathbb{R}$ defined by $\displaystyle f(x)=\frac{x^3}{3}-(2 a+3 b) x^2+24 a b x+5$ has a local maxima at -$\displaystyle 4$ and a local minima at $\displaystyle 4$ , then a value of $\displaystyle 4 a+3 b$ is