given analog signal :
x(t)=8cos(6,000pi)+5cos(14,000pit) t>=0
sampled at rate 12,000 Hz
a) sketch the spectorum of the orignal signal and the sampled signal from 0 KHz and 25 KHz.
b) sketch the recovered analog signal spectrum if an anti aliasing filter used.
c) determine the frequencies of aliasing noise , if any