Now, let's go back to the general NPV formula. We know that it looks like this. That NPV is equal to minus C sub 0 plus C1 or 1 plus R1 plus CK or 1 plus RK to the K power and so on and so forth. Well, what observations can we make? One we already made, we said that actually, C sub 0, we can spread over time. So that should not fall only here. But like I said, we can sort of incorporate that into some components of C1, CK, so and so forth. So this is not so very difficult. But for now, how can we proceed? Well, there are basically two ways. So let's look at this formula. We have Cs unknown and Rs unknown. Let's assume that Cs are known. Then, we can afford to play with Rs that vary. If however, Cs are not known, we can't hardly afford the luxury of playing with variable Rs. So we can say that R here is sort of constant. Now, this way leads us to the analysis of Bonds or better to say, the riskless bonds. And this is more applicable for stocks. Well indeed, for valuation of stocks, Rs also are not constant. But again, to deal with that is sort of a luxury because the uncertainty in Cs are so great that to a first approximation we can't ignore it. So that's how we proceed from here. Our second week is devoted to specifically these two cases. The first part is devoted to the analysis of again, government bonds and we will see that although Cs will be fixed. By the way, when Cs are known or fixed, this is the overall sub universe of so-called fixed income securities or fixed income instruments. These are the ones for which the Cs are forked. They are written down in a contract. So they are forecasted with a significant degree of certainty. That does not mean that the risky bond cannot default. In this case, the investor does not get all the promised amount of money. But we will limit our discussion when it comes to the second or next week only to riskless bonds. Here we will talk about the stocks. We will indeed say, well fine, we understand that this is a poor assumption. But we will still hold our constant and then we will try to analyze all these stories of growth or constant growth and we will see exactly where the value of a stock really comes from. So what is beyond? Beyond, this is the huge area of cases in which, first of all, everything is not constant. But even worse, when some of these Rs and Cs tend to change as a result of some changes in the environment. So if indeed we have these choices when we have the ability to make adjustments or forecasts, that opens up collegially a new, let's say, a paragraph or even a new chapter in valuation. That is all associated with options and other derivative securities that we study in greater detail in the further weeks of this course. So I'm wrapping up for now. I wish you all good luck with your assignments. There quite a few problems that although seem to be very straightforward but do require some time and effort. And it's very important that you solve these problems on your assignment because otherwise it will be not that clear for you what we'll be doing starting next week. So I wish you good luck again with these assignments and I see you next week.