Four travel on different sections of a long straight track. taking north to be positive direction, rank the trains in order by velocity, from most negative to most positive. the trains move as follows: train A moves north with a speed of 10 m/s. train B heads south and has twice the speed of train A. train C also heads south and has twice the speed of train A. train D travels north and covers 24m in 2 s. what is the answer?