Consider the system whose output \(y(m)\) is described as a function of the input \(x(m)\) by the following difference equations:

(a) \(y(m)=\sum_{n=-\infty}^{\infty} x(n) \delta(m-n N)\)

(b) \(y(m)=x(m) \sum_{n=-\infty}^{\infty} \delta(m-n N)\).

Determine whether the systems are linear and/or time invariant.