A particle is constrained to move along a straight line through O. it starts initially at D, which is a fixed distance from O in the positive direction and moves at a constant velocity of 4m/s for 15 seconds until it is 100m from O. It remains 100m from O for a further 25 seconds, after which it travels in the opposite direction for 20 seconds. the total distance traveled is 180m.
i) What is the velocity in the final stage of the journey? (2)
ii) What is the final displacement of the particle from its initial position? (2)