Suppose that analog voice has a bandwidth of 3.2 kHz and can therefore be served by the 4 kHz passband of twisted pair telephone wires. If each home telephone includes a digitizer that produces 64 kbps PCM voice (by using a 8000 samples/sec sampler, a 256-step quantizer, and an 8-bit encoder), then the 4 kHz of phone line channel must support a bit rate of 64 Kbps. Suppose that an M-level NRZ data encoder isused to achieve this. Assume that the signal design parameter a= 1,corresponding to rectangular pulses for representing the bits. Find the minimum M needed to fit the 64-kbps digital signal within the 4 kHz bandwidth.(Note: M must be power of 2)