In an experiment done by scattering 5.5 MeV α particles on a thin gold foil, students find that 10,000 α particles are scattered at an angle greater than 90 degrees.

Question

In an experiment done by scattering 5.5 MeV α particles on a thin gold foil, students find that 10,000 α particles are scattered at an angle greater than 90 degrees.
How many α particles will be scattered between 60 degrees and 80 degrees?