(Solved): 2. An Analog signal has frequency components at \( 1 \mathrm{kHz}, 12 \mathrm{kHz}, 28 \mathrm{kHz} ...

2. An Analog signal has frequency components at \( 1 \mathrm{kHz}, 12 \mathrm{kHz}, 28 \mathrm{kHz} \), and \( 30 \mathrm{kHz} \). The signal is sampled at a sampling rate of \( 20 \mathrm{kHz} \), then the resulting signal goes through an ideal reconstruction low pass filter (LPF) with a cutoff of \( 9 \mathrm{kHz} \). What frequencies are present in the output?