Solution (source code)

= Solution

For a nonnegative <random variable> $Z$ and $u>0$, <Markov inequality> states
$$
\boxed{P(Z\geq u)\leq\frac{\mathbb EZ}{u}.}
$$
It follows by taking expectations in $Z\geq u\mathbf1_{\{Z\geq u\}}$. A finite <expectation> makes the bound informative.