Particles moving in the magnetic field B experience two forces, the centrifugal force $($mv$2/$r$)$ and the Centripetal force provided by Lorentzian force $($qvB$),$ which are both perpendicular to its direction of propagation

$3$a$.$ Derive the magnetic rigidity equation using the relation between momentum and total energy.

$3$b$.$ Calculate the magnetic field B required to bend a $200$ MeV $12$C$4+$ beam using a dipole magnet with a bending radius of $2$ m$.$