Qualitatively write a mathematical expression applicable to a control volume for a generalized conservation principle typical for a macroscopic unsteady phenomenon. Fit the first and second law of thermodynamics into this framework. Then eliminating the floating quantity heat from the expression from the first law of thermodynamics and the $"$so called conservation" form of second law of thermodynamics labelled in the form of entropy generation rate arrive at the result that the lost available power is directly proportional to the rate of entropy generation.