 Solution

Introduce one shared GymStandings singleton object. It stores the latest current-performance score for every participating GymEquipment, using the equipment reference as key, and returns every equipment object tied for the maximum score. Performance.update sends each freshly computed score to this object. The previous observer pattern and its prediction observer remain in use.

The added Performance -> GymStandings dependency means “reports to,” while GymStandings -> GymEquipment represents the equipment keys in its stored score map. GymStandings is an software object, so clients share its unique instance instead of constructing one standings object per machine. The singleton pattern centralizes the current scores and the maximum-score query. Equipment objects, rather than user names, are the keys because two users can have the same name. Scores are current readings, not an accumulation of all historical notifications; the largest reported score wins, with all ties retained.