A particle P moves along a straight line. The speed of P at time t seconds (t > 0)is v= (pt² +qt +r) ms (where p. q and r are constants). When t = 2, the speed of P has its minimum value. When t = 0, v = 11 and when t = 2, v = 3. Find a) The acceleration of P when t = 3. b) The distance travelled by P in the third second of motion.