Okay, so let's do this problem. It says determine which face is the reface and which face is the side face. Okay? So we use the same prioritizing rules that we've been using before. Okay, but in this case, of course, this is an SB2 hybridized, not SB3 hybridized. So it's kind of a pro-chiral molecule. So the way we determine which is the reface and which is the side face of the face, the face facing this will determine the first. Okay? So we love, and we used to ask ourselves, what's bigger? Oxygen carbon or carbon? Of course, oxygen is. So we say, one, carbon, carbon. They're the same. Carbon or hydrogen? Well, that's two, and that's three. Like that. Okay? So if we see here, we go like this. Right? One, two, three. That's clockwise. Okay? Clockwise is the rebase. Okay? So we call this face that's facing this the reface. Okay? So let's drop the molecule. Let's put the molecule over and see the side face. Okay? So we'll do the same sort of analysis. Okay? So now we've looked the molecule over. We've got one, two, three, like that. Hopefully you see that's going counterclockwise there. So that's we call the side. Okay? Makes sense? Question on that one? No? Can I kill the video? Yes? Okay, wonderful.