The gain of an instrumentation ampifi er with differential inputs and outputs was measured at 6 kHz and 8 kHz in sequence with a 250-mV RMS input differential signal. The output at each frequency was found to be 0.88 V RMS and 0.95 V RMS, respectively. The differential inputs were then shorted together and the amplifier was again excited with a 250-mV RMS signal at 6 kHz and 8 kHz. The RMS level at the output at these two frequencies was 12 mV and 11 mV, respectively. Calculate the CMRR of this amplifi er at each test frequency.