A strip of doped silicon 260m wide contains 8.8 1022 conduction electrons per cubic meter and

Question:

A strip of doped silicon 260μm wide contains 8.8 × 1022 conduction electrons per cubic meter and an insignificant number of holes. When the strip carries a current of 130μA, the drift speed of the electrons is 44 cm/s. What is the thickness of the strip?