A system is described by the following differential equation, where $u(t)$ is the input to the system and $y(t)$ is the output of the system.
$$y(t) + 5y(t) = u(t)$$
When $y(0) = 1$ and $u(t)$ is a unit step function, $y(t)$ is
- $0.2 + 0.8e^{-5t}$
- $0.2 - 0.2e^{-5t}$
- $0.8 + 0.2e^{-5t}$
- $0.8 - 0.8e^{-5t}$