The lowpass signal x(t) with a bandwidth of W is sampled with a sampling interval of Ts, and the signal
is reconstructed from the samples, where p(t) is an arbitrary-shaped pulse (not necessarily time limited to the interval [0, Ts]).
1. Find the Fourier transform of xp(t).
2. Find the conditions for perfect reconstruction of x(t) form xp(t).
3. Determine the required reconstruction filter.