If $f$ is the functions whose graph is shown, let $h(x) = f \bigl( f(x) \bigr)$, $g(x) = f(x^2)$, $k(x) = \bigl( h(x) \bigr)^2$ and $\ell (x) = \bigl( g(x) \bigr)^2$. Use the graph of $f$ to estimate the value of each derivative.


a. $h'(2) \approx$       b. $g'(2) \approx$

c. $k'(2) \approx$       d. $\ell'(2) \approx$