A proton is accelerated from rest by a potential difference of 300 V. It then enters a magnetic field of magnitude 150 mt with its velocity perpendicular to the field. (q = 1.60 x 10-19 C, my = 1.67 x 10-27 kg) (A) (5 pts) Determine the speed of the proton. (B) (5 pts) What is the radius of its circular path in the magnetic field?