Ahall probe, consisting of a rectangular slab of current-carrying material, is calibrated by placing it in a known magnetic field of magnitude 0.15 t . when the field is oriented normal to the slab's rectangular face, a hall emf of 17 mv is measured across the slab's width. the probe is then placed in a magnetic field of unknown magnitude b, and a hall emf of 60 mv is measured. determine b assuming that the angle θ between the unknown field and the plane of the slab's rectangular face is