Task: Question Answering
Input (English): Problem: a person walks from one end to the other of a 90 - meter long moving walkway at a constant rate in 30 seconds , assisted by the walkway . when this person reaches the end , they reverse direction and continue walking with the same speed , but this time it takes 120 seconds because the person is traveling against the direction of the moving walkway . if the walkway were to stop moving , how many seconds would it take this person to walk from one end of the walkway to the other ? 
Options: a ) 36 , b ) 42 , c ) 48 , d ) 54 , e ) 60
Output (English): c