In a hall-effect experiment, a current of 3.7 a sent lengthwise through a conductor 1.5 cm wide, 4.0 cm long, and 12 μm thick produces a transverse (across the width) hall potential difference of 78 μv when a magnetic field of 0.76 t is passed perpendicularly through the thickness of the conductor.

a) find the drift velocity of the charge carriers and the number density of charge carriers.
b) show on a diagram the polarity of the hall potential difference.