What is the length of a running train crossing another 180 metre long train running in the opposite direction?

I.

The relative speed of the two trains was 150 kmph.

II.

The trains took 9 seconds to cross each other.

A. I alone sufficient while II alone not sufficient to answer
B. II alone sufficient while I alone not sufficient to answer
C. Either I or II alone sufficient to answer
D. Both I and II are not sufficient to answer
E. Both I and II are necessary to answer