1. The problem statement, all variables and given/known data
The Stratosphere Tower in Las Vegas is 1137 ft high. It takes 1 min, 20 s to ascend from the ground floor to the top of the tower using the high-speed elevator. The elevator starts and ends at rest. Assume that it maintains a constant upward acceleration until it reaches its maximum speed, and then maintains a constant acceleration of equal magnitude until it comes to a stop. Find the magnitude of the acceleration of the elevator.

The trip consists of two constant-acceleration segments, each of which has the same duration. You know the total displacement of the elevator.

2. Relevant equations
h = v_{0}t + 0.5at^{2}

3. The attempt at a solution
The last sentence makes me think the elevator accelerates to a certain speed, which it reaches half way up, and then decelerates with the same magnitude, stopping at the top.

This would mean
h = 568.5 = 0 +0.5(a)(40^{2}
a = 0.71ft/sec

I can't think of another way to solve this, but that isn't the correct answer.