From the top of a vertical tower 248 m high , a stone is projected vertically downwards with a speed of 8 ms . after x seconds another stone is projected vertically upwards from the level of the base of the tower with a speed 25 ms . given that two stones are at same height moving in the same direction 6 seconds after projection of the first stone , calculate : 1) value of x 2) the velocity of the second stone at this instant