A causal system having the transfer function $\mathrm{H}(s)=\frac{1}{s+2}$ is excited with $10 u(t)$. The time at which the output reaches $99 \%$ of its steady state value is
- $2.7 \; \mathrm{sec}$
- $2.5 \; \mathrm{sec}$
- $2.5 \; \mathrm{sec}$
- $2.1 \; \mathrm{sec}$