Can someone tell me how to do this?

What is the value of x in the diagram below?

An architect is designing a water fountain for a park she uses the given function to model the water jet flowing from the fountain nozzles where h(x) gives the height of the water jugs in feet x feet from the starting point h(x)=-1/20x+x+15

What is the arc length when θ =pi over 3 and the radius is 5 cm? (5 points) 5 pi over 3 cm 10 pi over 3 cm 16 pi over 3 cm pi over 3 cm