A narrow beam of protons with kinetic energy T = copper

A narrow beam of protons with kinetic energy T = 1.4 MeV falls normally on a brass foil whose mass thickness Pd = 1.5 mg/cm2. The weight ratio of copper and zinc in the foil is equal to 7: 3 respectively. Find the fraction of the protons scattered through the angles exceeding 00 = 30째.