Consider the following $2-$player sequential game:

Using the notation $($Ai$,($Bm$,$ Bn $))$ for the strategy profile, where Ai is A$\text{'}$s strategy and $($Bm$,$ Bn$)$ is $B^{\text{'}}$ strategy, where $Bm$ is the move to follow after $A1,$ and $Bn$ is the move to follow after A $2,$ answer:

The subgame perfect Nash equilibrium $($SPNE$)$ of this game is

There are potentially up to two other Nash equilibria in this game that are not SPNE: If existent, the Nash equilibrium that returns the same payoff as the SPNE is:

The Nash equilibrium that returns a different payoff is

If non existent, answer $"$NA$".$ Note that some games can have multiple SPNE, but the ones in these questions have been selected not to$.$