So let's think about what makes a valid probability model. One, the sum of the probabilities of all the scenarios need to add up to 100%, so we would definitely want to check that. And also, they would all have to be positive values, or I guess I should say, none of them can be negative values. You could have a scenario that has a 0% probability. And so all of these look like positive probabilities, so we meet that second test, that all the probabilities are non-negative, but do they add up to 100%? So if I had 0.2 to 0.5, that is 0.7 plus 0.1, they add up to 0.8, or they add up to 80%. So this is not a valid probability model.