# Theory Of Computation Test – Question 5

Consider the following Two lists $L_1,\,\,L_2$ of strings over alphabet $\Sigma&space;=&space;\left&space;\{&space;a,b&space;\right&space;\}$

$L_1&space;=&space;(abb,aa,aaa)&space;\,\,\,\,\,&space;L_2&space;=&space;(bba,aaa,aa)\textup{}$

The number of different Post Correspondence solutions for the above two lists is _________ .