A 1200 m long train crosses a tree in 120 sec, how much time will I take to pass a platform 900 m long?  Choose the most appropriate option.
A) 200 sec  B) 210 sec  C) 167 sec  D) 197 sec  E) 179 sec

Rationale: "l = s * t s = 1200 / 120 s = 10 m / sec . total length ( d ) = 2100 m t = d / s t = 2100 / 10 t = 210 sec answer : b"
Answer: B