Solution
= Solution
The other marginal is $X_2\sim N(\mu_2,\sigma_2^2)$ by the same square-completion argument with the indices exchanged. Its <moment-generating function> is therefore
$$
\boxed{M_{X_2}(t)=E[e^{tX_2}]
=\exp\left(\mu_2t+\frac{\sigma_2^2t^2}{2}\right),\qquad t\in\mathbb R.}
$$