Cities M and N are 600km apart. Bus A starts from city M towards N at 9AM and bus B starts from city N

Cities M and N are 600km apart. Bus A starts from city M towards N at 9AM and bus B starts from city N towards M at the same time. Bus A travels the first one-third of the distance at a speed of 40kmph, the second one-third at 50kmph and the third one-third at 60kmph. Bus B travels the first one-third of the total time taken at a speed of 40kmph, the second one-third at 50kmph and the third one-third at 60kmph. When and where will the two buses cross each other?

A.      300 kms from M

B.      280 kms from M

C.      305 kms from M

D.      295 kms from M