Use the​ maximum-minimum feature of your graphing calculator to determine the location of the peaks and valleys of f (x )equals 0.2 x cubed plus 0.3 x squared minus 1.2 x plus 0.4. a. Find the​ x-coordinates, if​ any, at which f has a peak​ (a maximum). What are these maximum​ values? b. Find the​ x-coordinates, if​ any, at which f has a valley​ (a minimum). What are these minimum​ values?