Find an expression for the discrete-time spectrum obtained by sampling a square pulse of unit amplitude and 1 ms in duration at a sampling rate of 10 kHz. If a discrete-time sequence with a frequency...

Find an expression for the discrete-time spectrum obtained by sampling a square pulse of unit amplitude and 1 ms in duration at a sampling rate of 10 kHz.

If a discrete-time sequence with a frequency of was obtained at a sampling rate of 10 MHz, what was the frequency of the original continuous-time signal (assuming no aliasing occurred)?