Consider the following signal y[n];
y[n] = X1[n+3] * X2[n]
The signals X1 and X2 are defined as
X1[n]=((1/2)^n) u[n]
X2[n]= ((1/3)^n u[n]
Determine the Z transform of y[n]. Furthermore, discuss wheter the signal is causal. Lastly, does the discrete-time Fourier transform Y(e^jw) exist for this y[n]?