The hall effect can be used to determine the density of mobile electrons in a conductor. a thin strip of the material being investigated is immersed in a magnetic field and oriented so that its surface is perpendicular to the field. in a particular measurement, the magnetic field strength was 0.875 t, the strip was 0.102 mm thick, the current along the strip was 3.89 a, and the hall voltage between the strip's edges was 1.59 mv. find the density of mobile electrons in the material.