V (mV) 250 200 150 50 0 -0.38 mm 2 V i=4 (Pxy) (Pxx) 3 4 5 Magnetic field (T) 6 V 7 3 10 8 0 V. (mv) Figure 1: Measured longitudinal and transverse voltages for a GaAs film at T = 1.2K. The applied current is I = - 25.5.. Ref. M. E. Cage et al., IEEE Trans. Instrum. Meas. IM-34, 301 (1985). (a) Use the low-field data (0 < B < 0.5T) in Fig. 1 to calculate the electron density and mobility. Note: the length L and width W of the Hall bar are indicated in Figure 1. (b) Use the high-field data (1T