ans is option 2) i.e value of root node is 7
on LHS subtree
min (7,9)=7 , min (6, unknown) <=6 and so max(7,<=6) =7
min(11,12)=11 min( unknown,unknown)=unknown and so max(11,unknown) >=11
and so min(7,>=11)=7
similarly on RHS subtree max possible value is <=5
finally at root max(7 ,<=5) =7