In a mass spectrometer, a beam of protons enters a magnetic field. Several protons make exactly a one-quarter circular arc of radius 0.50m. If the field is forever perpendicular to the proton's velocity, a) what is the field's magnitude if exiting protons have a kinetic energy of 10 keV? b) How long does it take the proton to complete the quarter circle? c) Discover the net force (magnitude) on a proton while it is in the field.