A 0.35 kg particle moves in an xy plane according to x(t) = - 12 + 4 t - 6 t3 and y(t) = 20 + 9 t - 11 t2, with x and y in meters and t in seconds. At t = 0.9 s, what are (a) the magnitude and (b) the angle (within (-180°, 180°] interval relative to the positive direction of the x axis) of the net force on the particle, and (c) what is the angle of the particle's direction of travel?