Once Rutherford and Geiger determined the charge-tomass ratio of the particle (Problem 71), they performed another

Once Rutherford and Geiger determined the charge-tomass ratio of the α particle (Problem 71), they performed another experiment to determine its charge. An α source was placed in an evacuated chamber with a fluorescent screen. Through a glass window in the chamber, they could see a flash on the screen every time an α particle hit it. They used a magnetic field to deflect β particles away from the screen so they were sure that every flash represented an alpha particle.
(a) Why is the deflection of a β particle in a magnetic field much larger than the deflection of an a particle moving at the same speed?
(b) By counting the flashes, they could determine the number of α s per second striking the screen (R). Then they replaced the screen with a metal plate connected to an electroscope and measured the charge Q accumulated in a time Δt. What is the a-particle charge in terms of R, Q, and Δt?