If 20 men can build a water fountain 56 metres long in 21 days, what length of a similar water fountain can be built by 35 men in 3 days? Select the correct option:
A) 10 m  B) 14 m  C) 17 m  D) 19 m  E) 20 m

Rationale: "explanation : let the required length be x metres more men , more length built ( direct proportion ) less days , less length built ( direct proportion ) men 20 : 35 days 21 : 3 : : 56 : x therefore ( 20 x 21 x x ) = ( 35 x 3 x 56 ) x = ( 35 x 3 x 56 ) / 420 = 14 hence , the required length is 14 m . answer : b"
Answer: B