So let's let X be equal to the number of defective chips in 500-chip sample. So the first thing to recognize is that this will be a binomial variable. This is binomial. How do we know it's binomial? Well, it's made up of 500, it's a finite number of trials right over here. The probability of getting a defective chip, you could view this as a probability of success. It's a little bit counterintuitive that a defective chip would be a success, but we're summing up the defective chips.