A 3 MeV fast neutron hits an alpha-iron target (threshold energy 40 eV, atomic wt. 55.85) creating a PKA. Find out the number of displaced atoms per PKA using a) simple K-P model, b) Snyder-Neufeld model, c) Sigmund's model, d) Lindhard's model, and e) channeling effect (Pch = 10%).