 Let's try another one of these dosage problems, but let's record this one this time. Actually, this one was sent in by Katie. So thanks, Katie, for the donation and the question. And Nick was the one who wanted us to record this one. So let's go ahead and record it for him. So, assume that you are a physician administering a drug in a solution containing 5.0 milligrams of drug per liter of solution. The recommended dosage of the drug is 3.5 times 10 to the negative 6 grams per kilogram of body weight. What volume of solution would you prescribe daily for a 68 kilogram patient? So, this is quite an involved problem and it gives us a lot of numbers. Let's go ahead and start by writing down the things that it gives us. So, it says that we are administering a drug in solution containing a concentration, so we'll just say concentration equals, this is the concentration of the drug, that equals 5.0 milligrams of the drug it says, per liter of solution like that. Remember, the way we like to do these is to take this, because that's like the text message way of writing it, and put it underneath. So one liter of solution. It also says that the recommended dosage of the drug is 3.5 times 10 to the negative 6 grams per kilogram of body weight. So, the dosage of the drug is going to be 3.5 times 10 to the negative 6 grams of the drug per, we can write that down, drug, and again it says per kilogram of body weight. But again, let's just rewrite this, so we'll say per one kilogram, and if we wanted to we could even say first. And the last thing it gives us is the weight of the patient. So the mass of the patient is 68, and then it asks what volume of solution would you prescribe for the daily dosage? Okay, so this is all the information we actually need in order to figure this out. So, in order to figure out the number of grams of the drug we're going to administer, we're just going to cancel out this because this is really kilograms of a person, right? We're just going to use this, combine with this, cancelling out the kilogram. So remember, this is on the top, this is on the bottom, so we can cancel out the kilograms of a person. So when we do that, first take out your calculator, and we're going to get 3.5 to the negative 6 times 10 to the negative 6, and we'll multiply that by 60, and it gives us 2.38 times 10 to the negative 4 grams of the drug. So that's how much we want to give on daily. Okay, but we have a solution concentration of this drug as 5 milligrams of the drug per liter of solution. So we're looking for this many grams. So we're going to have to, of course, convert milligrams to grams. So how do we do that? We take the conversion factor that you should know. 1,000 milligrams is one gram, cancel like that. And so then we're going to take, well, let's just do this first. So 5 divided by 1,000, of course, with 0.005 grams of the drug per one liter of solution. Okay, so we have this conversion factor that converts the mass of the drug to the volume of the solution that we're going to need. And here we have the total mass of the drug. So all we're going to have to do is just flip this conversion factor over and multiply it. Or in other words, divide this by this. So 1 liter of solution, 0.005 grams. It's actually going to be 5 zero grams of the drug. Because that zero will never remember to account for that safety. So that's going to cancel that. And all we've got to do is take our 2.38 to the negative 4 and divide that by 0.0050. When we do that, we get 0.0476 liters of solution. Of course, liters is not a very good unit to be applying to the patient. So we're going to put it into milliliters, something that's more recognizable in your syringe and whatnot. So how do we do that? We're just going to convert, of course, 1 liter, 1,000 milliliters, cancel, cancel. And then, of course, it's going to be 47.6 milliliters. And actually, this is not to the right number of significant figures, of course, because this has two significant figures, this has two significant figures, this has two significant figures. So with significant figures involved, we're going to round this up, this sticks up. So it's going to be 48.0. So that'll be the two signals. So Katie, I hope that answers your question. And I hope that the recording works well for you, Nick. And we will see you guys next time.