Consider the function $f(x)=\frac{1}{3} x^{3}$
(a) Use a graphing utility to graph the function and estimate the values of $f^{\prime}(0), f^{\prime}\left(\frac{1}{2}\right), f^{\prime}(1), f^{\prime}(2),$ and $f^{\prime}(3)$
(b) Use your results from part (a) to determine the values of $f^{\prime}\left(-\frac{1}{2}\right), f^{\prime}(-1), f^{\prime}(-2),$ and $f^{\prime}(-3)$
(c) Sketch a possible graph of $f^{\prime}$
(d) Use the definition of derivative to find $f^{\prime}(x)$