Solution
= Solution
{c}
From the preceding decomposition, $Y=(3/5)X+W$, where $W$ is independent of $X$ and has mean zero. Taking <conditional expectation> gives $\mathbb E[Y\mid X]=(3/5)X$. The corresponding continuous version at $X=5$ is
$$
\boxed{\mathbb E[Y\mid X=5]=3.}
$$