4.2-6 Two signals my (f) and m2(1), both band-limited to 5000 Hz, are to be transmitted simultaneously over a channel by the multiplexing scheme shown in Fig. P4.2-6. The signal at point b is the multiplexed signal, which now modulates a carrier of frequency 20,000 Hz. The modulated signal at point c is transmitted over a channel. (a) Sketch signal spectra at points a, b, and c. (b) What must be the bandwidth of the distortionless channel? (e) Design a receiver to recover signals m₁ (1) and m2 (1) from the modulated signal at point c.