Please help me solve this the way my professor solved

Problem 4: Loma Linda university uses a proton beam to treat cancer (m. =1.602-10 "-kg). Below is a diagram of the basic set up. In this problem we will explore how the proton beam can be targeted at a particular point to treat cancer. The cydotron accelerates the proton up to an energy of / 250. 10" . where an electron volt is defined as ev = 1.602 - 10 " J. (a) What is the speed of the particle (hint think Kinetic energy(b) what is the radius of the beam if the maximum field is given by B. :5.58-T (See problem 2 and 3 ) (c) What is the radius of the beam if a small field of B. = 100.00 - 10 7' is used (note this is about 3 times the earth magnenc fled) (d) Using the difference between c and d said another way what is the range of beam radio Ke = (4.005 - 10 ) 171= 2. 4 (2.236-10) C " - (1.936 - 10 m d ARE=RIM - Rin = (1.936 - 10 ) m