All the statements are true with respect to the concept of 'EFFICIENCY' as used in the mainstream economics. Economic efficiency implies an economic state in which every resource is optimally allocated to serve each individual or entity in the best way while minimising waste and inefficiency. Efficiency occurs when no possible reorganisation of production can make anyone better off without making someone else worse off. An economy is clearly inefficient if it is inside the Production Possibility Frontier (PPF). At a minimum, an efficient economy is on its Production Possibility Frontier (PPF).