Now rule number one we call the product rule. And rule number two we call the sum rule. So let's begin by defining what, what the product rule is. So the product rule states that the probability of two or more independent events taking place or occurring is equal to the product of their individual probabilities. And that's exactly why we call the product rule the product rule because it involves the word product. So to calculate or to use the product rule, we actually have to multiply the individual probabilities as we'll see in just a moment.