 So, before we start analyzing a simple system, it is best to know how many inlets and outlets should one consider for an open system. Technically one considers an open system can have an infinite number of inlets and exits. For example, if I take an imaginary control volume in this room, at every point of the surface of this imaginary volume, air is either going into the system or going out of the system. And the flow need not be uniform at any point. If one wants to know the total amount of mass going in and out, one will have to integrate over the entire surface and get the quantity right. However, one could always look at systems which have a single inlet and outlet. For example, water flowing through a duct or a pipe could be analyzed as a system with one inlet and one outlet. One could also analyze turbines and compressors similarly. For a system such as a boiler, depending on how one analyzes, one could have a single or multiple number of inlets and outlets. Now, even across the single inlet and outlet, one can assume that the flow is uniform, that is have it as a one-dimensional flow into the system and a one-dimensional flow out of the system. Or one could try to analyze it correctly and integrate the amount of mass coming into the system by integrating across that single inlet assuming that the flow coming in is not uniform. Thus, once we look at all of this, we can have an open system which could be like this, where across all the points, one could be seeing mass coming in and out as such. So, this such a system has an infinite number of inlets and exits or one could look at a system which probably I will just draw an arbitrary open system and one could have an inlet here and inlet here and exit here and exit here. So, I have a discrete amount of inlet and exit. So, as I said before, we could have the flow coming in uniform here or we could have some kind of a variation in which case we would need to integrate the flow that comes in. Thus, one has to realize that depending on the system, we can have an infinite number of inlets and exits or a finite number that can be enumerated. What we will do when we consider a simple analysis is we will consider only a single inlet and a single outlet and then one can see that you can go ahead and generalize such a system. So, that is what we will take up in the next lecture. Thank you.