From A: Knowing only that exactly one bye occurred in the tournament narrows possibilities, but without knowing which round, multiple \(n\) values are possible in the 65–128 range.
From B: Knowing only that the bye occurred in round 3 → round 4 also does not fix \(n\) uniquely, because different initial \(n\) can produce a bye in that round.
Together: The round of the bye plus its uniqueness allows exact backtracking of eliminations to find initial \(n\). This yields a unique \(n\).
Thus, both together are sufficient, neither alone is.