If   $A\left(Z_1\right) , B\left(Z_2\right) , C\left(Z_3\right)$ and $D\left(Z_4\right)$  are four points in Argand plane such that $Z_1,Z_2,Z_3,Z_4$  are roots of the equation  $Z^4-5Z^3+18Z^2-17Z+13=0$  and $\left|Z_1\right|\ne \left|Z_2\right|$. Let P be the point of intersection of line  $Z(i+\sqrt{3})+\overline{Z}(\sqrt{3}-i)-2\sqrt{3}=0$  with real axis, then the value of 
[PA.PB] is equal to___________
(Where [.] is greatest integer function)