1. The problem statement, all variables and given/known data Telephone calls enter a college switchboard according to a Poisson process on the average of three calls every 4 minutes (i.e., at a rate of λ=0.75 per minute). Let W denote the waiting time in minutes until the second call. Compute P(W>1.5 minutes). 2. Relevant equations 3. The attempt at a solution I don't get it. No idea how to do it. I guess 1.5 means here that at the most 1 event can occur here.