Determine whether each of the following processes $X(t)$ is invertible, justifying your conclusions:
Part (a)
$X(t) = Z(t) - 0.4Z(t-1).$

A. Invertible.
B. Non-invertible


Part (b)
$X(t) = Z(t) - 0.7Z(t-1) + 0.3Z(t-2).$

A. Non-invertible
B. Invertible.