 Okay, so let's do this one. It says calculate the units or degrees of unsaturation in the following molecular formula, okay? And then it says C25H27BrFnO7S2, okay? So do you remember what we do in order to do the units of unsaturation? Right. Yeah, we've got to take each of these ones and decide how it adjusts the number of hydrogens here that we're going to, right? Okay, so for the halogens, right, we have two of them, bromine and fluorine. What do we do to the number of hydrogens when we have a halogen? Add one. Add one, right? Okay. So since we have two, we're going to add two hydrogens, right? So plus one hydrogen, plus one hydrogen, like that. And with nitrogen, what do you do? Subtract one, right? So minus one hydrogen. Oxygen, what do you do? Nothing, right? So even though we have seven of them, you just cancel that out, okay? And what about sulfur? Same thing, right? Because that's like oxygen's big brother, so he does the same thing, oxygen. So we have all those cancelled out, and all we have to do is now add two hydrogens and then subtract one. So 29 and then 28, right? So our new molecular formula is C25H28, right? Does that make sense? Okay. So now what's the next step that we've got to do? Formula. Yeah, the formula for the saturated alkanes, right? Do you remember what that formula was? Cn. Yes, there you go, C9 plus 2, like that, okay? So we have n is 25, right? So we've got to go over here, C25H, what is that going to be? 25 times 2, 50 plus 2 is 52, right? H52, like that. Is that what we have over here? H52? No. No way, we have H28, so what are we going to do now? Subtract, right? The C's will always cancel, right? And what do we have here? 52 minus 28. Can you do that in your head? So this is like 50 and 30, right? So that's 24, isn't it? I think it's 24. Yeah. Is that right? Yeah, it's 24. Okay, so H24. So that's how many hydrogens we're missing, but that translates to how many units of unsaturation. Do you remember what we do up there? Okay, so we have to take this number and divide it by 2 because for every unit of unsaturation, you're missing two hydrogens, okay? So since we're missing 24 hydrogens, how many units of unsaturation do we have? 12. 12, okay? So just take that if you want to and divide it by 2 and that equals 12 units. It seems a little more daunting than it really is. When you look at this, it looks dirty, you know, at the beginning, when you just start doing the math, it's not so good. Okay, does that make sense? Yeah. Okay, wonderful. Any other questions? Not easy. Okay, wonderful.