将解释与方程式结合起来

Question

我目前正在尝试编写解决方案手册。为了使它看起来更整洁，我尝试将解决方案组织成一个框中的列（使用带有多列的 mdframed）。

这是我现在得到的。有什么方法可以将解释与方程式对齐吗？我尝试过文本和互文，但似乎不起作用。

提前致谢！

\documentclass{exam}
\usepackage[utf8]{inputenc}
\usepackage{multicol}
\usepackage{markdown}
\usepackage{lipsum}% dummy text
\setlength{\columnsep}{1cm}
\usepackage{amsmath} 
\usepackage{enumitem}
\usepackage{graphicx}
\usepackage{mdframed}

\begin{document}

\maketitle

\begin{questions}
 
\question A man of mass $60kg$ stands on a weighing machine, which is placed on the floor of a lift. When the lift is moving upwards with an acceleration of $0.5ms^{-2}$, the reading of the weighing machine would be? (Take $g = 10ms^{-2}$)

  \begin{oneparchoices}
    \choice $570N$
    \choice $600N$
    \choice $605N$
    \choice $630N$
    \choice $770N$
  \end{oneparchoices}

\noindent \textbf{Solution:}

\begin{mdframed}
\begin{multicols}{2}

Consider the man as a system. 
\begin{equation*}
\begin{aligned}
\text{By }\sum \vec F &= m \vec a\\
N - mg &= ma\\
N &= mg + ma\\
N &= 60(10+0.05)\\
N &= 630(N)\\
\end{aligned}
\end{equation*}

\columnbreak

\includegraphics{Q2_1.png}

\end{multicols}
\end{mdframed}


\end{questions}

\end{document}