A building 4.8 m high 2b meters wide has a flat roof. A ball is projected from a point on the horizontal ground 14.4 metres away from the building along its width. If projected with velocity 16 metres per second at an angle of 45 degrees with the ground , the ball hits the roof in the middle , find the width 2b. Also find the angle of projection so that the ball just crosses the roof if projected with velocity 10 root 3 m/s.