You will also often find that exercises in other textbooks and in online WeBWorK will just provide \(\lambda\) for the underlying Poisson process and that the time interval T will be presumed to be T=1. For those problems, if the exercise asks for a Poisson probability, use \(\mu = \lambda\) while if the exercise asks for an Exponential probability, use \(\mu = \frac{1}{\lambda}\text{.}\)