A proton moves in a helical path at speed v = 4.0 107 m/s high above

Question:

A proton moves in a helical path at speed v = 4.0 × 107 m/s high above the atmosphere, where Earth's magnetic field has magnitude B = 1.0 × 10−6 T. The proton's velocity makes an angle of 25° with the magnetic field.
(a) Find the radius of the helix.
(b) Find the pitch of the helix-the distance between adjacent "coils."