Consider the cascaded system as shown in the figure. Neglecting the faster component of the transient response, which one of the following options is a firstorder pole-only approximation such that the steady-state values of the unit step responses of the original and the approximated systems are same?
- $\frac{1}{s+1}$
- $\frac{2}{s+1}$
- $\frac{1}{s+20}$
- $\frac{2}{s+20}$