Are all instances of the $8-$puzzle games solvable?

$2.$ Provide an upper bound on the size of the state space in the N$-$puzzle game? Consider only

reachable $($solvable$)$ configurations. A tight bound will receive extra credit.

Hint: You should determine the total number of possible configurations as the first step.Then

determine the tight bound for total number of solvable states which is the final answer