(a) A proton, traveling with a velocity of $4.5 \times 10^{6} \mathrm{m} / \mathrm{s}$ due east, experiences a magnetic force that has a maximum magnitude of $8.0 \times 10^{-14} \mathrm{N}$ and a direction of due south. What are the magnitude and direction of the magnetic field causing the force? (b) Repeat part (a) assuming the proton is replaced by an electron.