A horizontal metal strip 1.0 mm thick and 20 mm wide carries a 21-A current along its length, and both the length and the width are perpendicular to a uniform magnetic field of magnitude 2.0 T that is directed vertically up. The potential difference across the strip width is 4.27 μV.

PART A: If the side of the strip width that is to your left as you look in the direction of the current is at the higher potential, what is the sign of the mobile charge carriers?

Positive or Negative

PART B: What is the speed of the charge carriers?

PART C: What is the number density of the charge carriers? (express your answer in m^-3)