When a particle of charge q and momentum p enters a uniform magnetic field at right angles

Question:

When a particle of charge q and momentum p enters a uniform magnetic field at right angles it follows a circular path of radius R = p/qB, as shown in FIGURE 29-35. What radius does this expression predict for a proton traveling with a speed v = 0.99c through a magnetic field B = 0.20 T if you use

(a) The non relativistic momentum (p = mv) or

(b) The relativistic momentum (p = mv (1 - v2 / c2)

Figure 29-35