Where do combinations that are possible but inefficient lie in relation to the production possibilities frontier?

Combinations that are possible but inefficient lie inside the production possibilities frontier (PPF). The PPF illustrates the maximum possible output combinations of two goods or services that an economy can achieve when all resources are fully employed and used efficiently. Any point that lies inside this frontier indicates that the economy is not utilizing all its resources effectively or is not achieving the maximum possible production capacity. Therefore, those combinations represent inefficiencies where more of one or both goods could be produced without having to sacrifice the production of the other. In contrast, points on the frontier indicate efficiency, where all resources are fully utilized, and points outside the frontier are unattainable with the current resources and technology.