So this is going to be, when does x times x minus 3 equal 0? Well, if the product is equal to 0, at least one of these need to be equal to 0. So x could be equal to 0, or x minus 3 is equal to 0. So x is equal to 0, or x is equal to 3. So this is x is 0, and this right over here is x is equal to 3. So that gives us our interval. We're going to go from x equals 0 to x equals 3 to get our volume.