Maximization of utility

1-When discussing the maximization of utility, regardless of whether you chose to work more hours or fewer when offered a higher hourly wage, you could not be wore off than you were at a lower hourly wag. Can show this?2- People join tennis clubs for a fixed fee per year, which entitles them to play as much as they want without change. Because people who pay these fees ply more tennis than others ( who can use free public courts), this means sunk costs matter for decisions. Right? 3- How does the existence of money reduce the costs of making transactions relative to a society based entirely on barter? English is becoming the usual language for international transaction, even if the language of neither country is English. How does this reduce the cost transacting?