A roller coaster is designed such that riders experience "weightlessness" as they go round the top of a hill whose radius of curvature is 20m. The speed of the car at the top of the hill i between -

Question

( A ) 15 m/s and 16 m/s
( B ) 13 m/s and 14 m/s
( C ) 16 m/s and 17 m/s
( D ) 14 m/s and 15 m/s