5. y=x -3x -24x+4. a) (12 pts) Find (x, y) coordinates at which the tangent line is horizontal. Use 3 decimal place accuracy as needed. Be sure to show all analytic work. b) (2 pts) What is the equation of the tangent line at each of the points found is part a)? c) (4 pts) Set up appropriate window settings and graph the original function and label the (x.y) coordinates of the points found on your graph. State your Xmin, Xmax, Ymin and Ymax settings used