A 290 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?  Choose the correct choice from the following answers:
A) 230 m B) 210 m C) 260 m D) 320 m E) 330 m

Rationale: "relative speed = ( 120 + 80 ) km / hr = ( 200 x ( 5 / 18 ) ) m / sec = ( 500 / 9 ) m / sec . let the length of the other train be x metres . then , ( x + 290 ) / 9 = 500 / 9 x + 290 = 500 x = 210 . b"
Answer: B