 Welcome back, now let us try to consider a system containing water in some form, a system containing what we in thermodynamics can call an ordinary water substance or in general we will call a system which contains water or steam and again which is at rest. Now we know from the lectures of Professor Atrey that such a system does not have a simple straight forward easily usable equation of state. We have a large amount of data which has been fitted but that is a very very complex state of FS, we have a complicated set of equations of state relation between P, V and T relation between U and P and T relation between H and P and T relation between S and P and T and water. So because of this complexity we have no choice but to use steam tables and I hope you would have become familiar with steam tables already in the exercises that Professor Atrey assigned to you. So when we solve problems using second law which we will do soon, you will have to look up properties and entropy also along with other properties. So what is recommended is that review the lectures by Professor Atrey where he has talked about phases of steam, properties of steam with particular interest in entropy wherever he mentions entropy or even if he does not mention now look at the entropy columns with some interest, you will have to read those also. And in particular look at what he says about Mollier diagram particularly the HS diagram that is a very good visual expression. Thank you.