 So it says, Polonium metal crystallizes in a simple cubic unit cell with an edge, the length, of 334 picometers. What is the radius of a Polonium atom? Okay, so if you recall, simple cubic atom on each one of those corners. So if we were to blow that part up, right, it would be 2R equals X. So the formula that we know for the simple cubic is 2R equals X, and it gave us the length of the side, which is S, right? So S equals 334 picometers. And it's asking us, well, what's the radius of the Polonium atom? Well, in this case, right, the radius is going to be R of the Polonium. So R Polonium equals S divided by 2. So S is 334 picometers, and it wants this in picometers. So 334 divided by 2 is going to be 167 picometers. So the 3, 6. So is everybody okay with that? Remember what we did when we blew this part up here, kind of think of that as being R and R. This is the whole side thing. So 2R equals the side. So that's how you do it for the simple cubic. Are there any questions on that one? So if you can't remember that, just memorize those ones.