What is the Nash Equilibrium in the above matrix?

O $1)$ Fim A charges $510$ and Firm B charges $515$

$21$ Firm A charges $$10$ and Firm B charges $510$

$7.$

$03)$ Frm Acharges $515$s and Firm B charges $$10$

$04)$ Frm A charges $515$ and Firm B charges $51\mathrm{.}5$