Answer:
The height of the beam is: 
Step-by-step explanation:
The radius of the tunnel is r = 15 feet
The distance of the beam from the center of the tunnel is:

We have a right triangle, where:
- The Hypotenuse is 15 feet
- One side is 9 feet
- The other side is the height of the beam
Let's use Pythagoras theorem.



Therefore, the heigh of the beam is:

I hope it helps you!