In Figure 20.12, a small particle of charge q = -7.0 x 10^-6 C and mass (m = 3.1x10^-12) has velocity (Vo = 9.4x10^3 m/s) as it enters a region of uniform magnetic field. The particle is observed to travel in the semicircular path shown, with radius r = 5 cm. Calculate the (a) magnitude and (b) direction of the magnetic field in the region.