Samantha values the utility of her first cup of coffee at $1.00, a second cup, 50.75; and a third cup, 50.50. If Samantha drinks three cups of coffee for breakfast, her marginal utility is equal to_________
O $0.50, the value of her last cup of coffee.
O $1.00, the value of her first cup of coffee.
O $2.25.
O $1.50.