Answer
See answers.
Work Step by Step
a. See figure 30–17. The initial force on the rightward-moving particle is down. Apply the right-hand rule. With the magnetic field going into the page, the force on a positively-charged particle would be upward.
The particle must be negatively charged. It is $\beta^-$ decay.
b. Assume that the particle is not relativistic. Use equation 20-12, r = mv/qB. Solve for the speed.
$$v=\frac{qBr}{m}=\frac{(1.60\times10^{-19}C)(0.012T)(0.0047m)}{9.11\times10^{-31}kg}=9.9\times10^6 m/s$$
Indeed, this is a nonrelativistic speed.