Solution
= Solution
A <Poisson process> has a <Poisson distribution> for the count in an interval of length $t$, with mean equal to rate times length. Fifteen minutes is $1/4$ hour, so
$$
\boxed{N(5{:}15)-N(5{:}00)\sim\operatorname{Poisson}(3),\qquad\mathbb P(N=k)=e^{-3}\frac{3^k}{k!},\quad k\geq0.}
$$