4.2-10 A DSB-SC signal is given by m(t) cos (27)10r. The carrier frequency of this signal, 1 MHz, is to be changed to 400 kHz. The only equipment available consists of one ring modulator, a bandpass filter centered at the frequency of 400 kHz, and one sine wave generator whose frequency can be varied from 150 to 210 kHz. Show how you can obtain the desired signal cm(t) cos (27 x 400 x 10r) from m(t) cos (27)10r. Determine the value of c.