 We are going to be making the same four assumptions to pretty much all of our gas power cycles. So frequently will we use these in fact that we give them a special name. They are called the air standard assumptions. The air standard assumptions are made up of four assumptions. They are one that the working fluid is air and behaves as an ideal gas. We are also assuming that that air is the same air throughout the entire cycle. Like in a reciprocating engine we are intaking the same air that we just exhausted. Two, we are treating the combustion process as an external heat addition process. Three, we are replacing the exhaust process with a heat exhaustion process. And we are four assuming that all processes are internally reversible. So when we use all four of these assumptions we call it an air standard analysis. One additional assumption that we tack onto this is the assumption of constant specific heats evaluated at 300 Kelvin. That fifth assumption turns this from the air standard to the cold air standard. So when you see cold air standard that is referring to these four, plus the assumption of constant specific heats evaluated at 300 Kelvin.