Assuming a continuous signal is given as
Sampled at a rate of 8,000 Hz,
a. Sketch the spectrum of the sampled signal up to 20 kHz;
b. Sketch the recovered analog signal spectrum if an ideal low pass filter with a cutoff frequency of 4 kHz is used to filter the sampled signal in order to recover the original signal;
c. Determine the frequency/frequencies of aliasing noise.