p is equal to lambda divided by n. I just rearranged this up here, right? So our probability of success is lambda times n. And we're saying, what's the probability that we have k successes? And then what's the probability that we have a failure? Well, it's 1 minus the probability of success. And how many failures are we going to have? How many moments will not have a car pass? Well, we have a total of n moments, and k of them were successes.