While reproducing the Rutherford scattering experiment in an advanced laboratory class, a student uses a gold foil with thickness 15.6 nm. The radioactive source emits particles at 6.40 MeV, and the detector is placed at 29.9 cm from the target foil. What fraction of the particles is detected per unit area at an angle of 18.1?

What fraction of the particles will scatter to the angle given above or higher?