Characterize the systems below as linear/nonlinear, causal/noncausal and time invariant/time varying:

(a) \(y(n)=(n+a)^{2} x(n+4)\)

(b) \(y(n)=a x(n+1)\)

(c) \(y(n)=x(n+1)+x^{3}(n-1)\)

(d) \(y(n)=x(n) \sin (\omega n)\)

(e) \(y(n)=x(n)+\sin (\omega n)\)

(f) \(y(n)=\frac{x(n)}{x(n+3)}\)

(g) \(y(n)=y(n-1)+8 x(n-3)\)

(h) \(y(n)=2 n y(n-1)+3 x(n-5)\)

(i) \(y(n)=n^{2} y(n+1)+5 x(n-2)+x(n-4)\)

(j) \(y(n)=y(n-1)+x(n+5)+x(n-5)\)

(k) \(y(n)=(2 u(n-3)-1) y(n-1)+x(n)+x(n-1)\).