11.9. A GaAs wafer with a thin N-type epitaxial layer is measured with a 6-contact Hall structure as shown in Fig. 11.17 whose critical dimensions are f = 200 um and w = 50 um. For a bias current of 1.00 mA, the measured voltages are V. = 1.42 V and, with a magnetic field of 0.6 Tesla, VH = 93.7 mV. (a) What is the sheet resistance Rs of the conductive layer? (b) What is the electron mobility An? (c) What is the surface electron density ns