In quadrilateral $PQRS$, $PS$ $=$ $5$, $SR$ = $6$, $RQ$ $=$ $4$, and  $\angle P = \angle Q = 60°$. Given that

$2$$PQ$ $=$ $a$ $+$ $\sqrt b$ , where $a$ and $b$ are unique positive integers, find the value of $a$ $+$ $b$.