Solve the all parts of following problem:
Problem: A Hall-effect probe operates with a 120 -mA current. When the probe is placed in a uniform magnetic field of magnitude 0.0880 T, it produces a Hall voltage of 0.760 µV.
Part A: When it is used to measure an unknown magnetic field, the Hall voltage is 0.400 µV. What is the magnitude of the unknown field?
Part B: The thickness of the probe in the direction of B is 2.20 mm. Find the density of the charge carriers?
I need help to find the density of the charge carriers.