Notice that h(x) is a cubic function. Visualize its graph.
consequently, it is the location of a local max or min of h(x).
Since h(x) is a cubic function, there should be another local max or min. Find its location by setting h '(x) = 0 and solving for x.
Recall that maxima and minima are y-values. So evaluate h(x) to find the corresponding y-values.