The motion of a particle is defined by the equations s x = 6 − 0.8t (t2 − 9t +18) and y = − 4 + 0.6t (t2 − 9t + 18), where x and y are expressed in meters and t is expressed in seconds. Show that the path of the particle is a portion of a straight line, and determine the velocity and acceleration when
(a) t = 2 s,
(b) t = 3 s,
(c) t = 4 s.