Need Help with #9 :(

Whats the name of the vertical axis

Atheater wants to build movable steps that they can use to go on and off the stage. they want the steps to have enough space inside so they can also be used to store props. how much space is inside the steps?

Two poles, ab and ed, are fixed to the ground with the of ropes ac and ec, as shown: what is the approximate distance, in feet, between the two poles? 6.93 feet 8.66 feet 12.32 feet 15.59 feet