Now, suppose that you have a balanced stereo signal in which the left and right channels have the same voltage amplitude, 500 mVpp. This time, however, you want to be able to mix these two channels into a single inverted output while independently varying the gain of the two channels. Design and build an op amp circuit with potentiometers so that you can independently vary the gain of the left and right channels. Choose resistors so that the overall output of your circuit ranges between 0.1Vpp (when both channels are set to minimum gain) and 20Vpp (when both channels are set to maximum gain).