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?	Select the correct option:
A) 36 B) 42 C) 48 D) 54 E) 60

Rationale: "let v be the speed of the person and let x be the speed of the walkway . 30 ( v + x ) = 90 then 120 ( v + x ) = 360 120 ( v - x ) = 90 when we add the two equations : 240 v = 450 v = 15 / 8 time = 90 / ( 15 / 8 ) = 48 seconds the answer is c ."
Answer: C