How can there be most happiness?
Bentham thought that 'the good is whatever brings the greatest happiness to the greatest number of people', the Greatest Happiness Principle. This principle is strong, as it would seem to include all of the future, which, however has often proven difficult to put to practice, probably not least because predicting the future is infeasible.
Asking 'how there can be most happiness in a specific situation' when weighing different choices would seem the same utilitarian / consequentialist perspective.
Assuming, however, 'can' independently of a specific situation, would open the perspective of what can be possible within the limits of reality in order to get information on possible goals. This would avoid the necessity of prediction. The difference between our understanding of reality and reality itself remains, and practical implementation of such goals would still require decisions, but this question could add a useful perspective.