For a closed-loop system, consider the following transfer functions:

process $G_{p}\left ( s \right )$, controller $G_{c}\left ( s \right )$, measuring device $G_{m}\left ( s \right )$, and final control element $G_{f}\left ( s \right )$

$$G_{p}\left ( s \right )=\frac{2}{7s+1};\: G_{c}\left ( s \right )=2; \:G_{m}\left ( s \right )=1; \: G_{f}\left ( s \right )=1$$

The offset in the closed loop response due to a unit step change introduced in the set point of the output variable is ___________.