There are ten analog signals, each of bandwidth B=4kHz. Samples of these signals are time-division-multiplexed, quantized and binary-coded. If the number of quantization levels L is 200, the step size Δ of the quantizer is equal to (%) of the peak amplitude mmax. If the transmission bandwidth BT is 640kHz, the Nyquist criterion pulse with roll-off factor a= should be used, where the sampling rates must be at least 50% above the Nyqusit sampling rate.