This is another 20k potentiometer wired as a voltage divider to provide attenuation (volumecontrol).Block 4:In a previous lab (lab 6), we had a two LED voltage level indicator. If you extend this to 4 levels, that becomes Block 4. The input to Block 4 is a mono audio signal which will typically be about400mVpp (but could be as high as 1.2Vpp depending on the input signal). For Block 4, design a4 level voltage meter using comparators and LEDs. For the reference voltages, divide down the+9V power rail into references of approximately 120mVdc, 80mVdc, 60mVdc, and 20mVdc. These reference values were chosen to give a lively LED display for most music audio signals. Since the LF412 Op-amps used for comparators in this block are only supposed to be able tooutput 20mA, design this block assuming that 10mA will be the maximum current allowedthrough the LED when it is lit. Keep in mind: The sum of the resistors must be in the kΩ region or too much current will bedrawn from the 9 volt source. Hold the total current to about 0.1 mA (100 μA).