Futuroscope

 

This pavilion of the Futuroscope (French theme park) was built in 1991. It is made up of a right prism and a sphere with radius 8.5 m. Its visible part on the roof is a spherical cap with height 13.60 m.

  What is the radius of the sectional circle
of the spherical cap with the roof in metres,
to the nearest tenth?