Consider a system with transfer-function \( G(s) = \frac{2}{s+1} \). A unit step function \( \mu(t) \) is applied to the system, which results in an output \( y(t) \). If \( e(t) = y(t) - \mu(t) \), then \( \lim_{t \to \infty} e(t) \) is \(\underline{\hspace{2cm}}\).
