A system executes a power cycle while receiving Q_H by heat transfer at a fixed temperature of T_H and discharging Q_C by heat transfer at a fixed temperature of T_C. There are no other heat transfer processes in the cycle. a. The thermal efficiency of a power cycle can be evaluated as:
b. For this power cycle, the Clausius Inequality reduces to:
c. If σcycle is has a negative value, the cycle is:

attach the statements so i can answer : )

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

k2s for potassium sulphide