In a linear accelerator, protons are accelerated from rest through a potential difference to a speed of approximately 2.74 x 10^6 m/s. The proton beam enters a region of uniform magnetic field B as shown below, which causes the beam to follow a semicircular path. Determine the magnitude of the field that is required to cause an arc of radius 0.158 m. The charge of the proton is 1.60 x 10^-19 C, and the mass of the proton is 1.67 x 10^-27 kg. The proton beam enters the magnetic field with a velocity vector perpendicular to the page.