Functions $F(a,b)$ and $G(a,b)$ are defined as follows:

$F(a,b)=(a-b)^{2}$ and $G(a,b)=\mid a-b\mid ,$ where $\mid x\mid$ represents the absolute value of $x.$

What would be the value of $G(F(1,3),G(1,3))?$

1. $2$
2. $4$
3. $6$
4. $36$

edited