我如何在 LaTeX（回忆录）中实现这样的布局？

Question

在“练习 1.2”之前，页面有单独的“边注”和“正文”，但之后，“正文”似乎与“边注”合并了。我希望我的书上有类似的布局。

\documentclass[10pt]{memoir}
\setstocksize{10in}{8.5in}
\setpageml{0.9\stockheight}{0.9\stockwidth}{*}
\setlrmarginsandblock{1in}{2in}{*}
\setulmarginsandblock{0.75in}{0.75in}{*}
\checkandfixthelayout[fixed]

\usepackage[]{showframe}
\usepackage{graphicx}
\usepackage{xsim}

\begin{document}
\chapter{Lorem Ipsum}
\lipsum[1]

\marginparmargin{outer}
\marginpar{%
\centering
\includegraphics[width=4cm]{example-image-a}}

\begin{exercise}    %   this environment needs to typeset throughout the paper width
\lipsum[2]
\end{exercise}
\end{document}