How to make a shaded box like this picture using tcolorbox

Question

\documentclass{jsarticle}
\usepackage[dvipdfmx]{graphicx}
\usepackage{tikz,tcolorbox,color} 
\tcbuselibrary{skins}
\usetikzlibrary{calc} 
\usepackage{amsmath}
\usepackage{color}
\usepackage{tcolorbox}
\tcbuselibrary{breakable,theorems,skins}
\usetikzlibrary{calc}
\newenvironment{renumerate}{\renewcommand{\labelenumi}{%
（\arabic{enumi}）}\begin{enumerate}}{\end{enumerate}}

\newcount\K                                                           
\def\ksfor#1{
\K=#1                                                                            
 \ifnum\K=5                                
\textcolor{ored}{★★★★★}
\fi
\ifnum\K=4                                
\textcolor{ored}{★★★★☆}
\fi
\ifnum\K=3   
\textcolor{ored}{★★★☆☆}                             
\fi
\ifnum\K=2     
\textcolor{ored}{★★☆☆☆}                           
\fi
\ifnum\K=1                                
\textcolor{ored}{★☆☆☆☆} 
\fi
}

\definecolor{ored}{rgb}{0.5, 0.0, 0.13}
\newcounter{reidai}
\setcounter{reidai}{52}

\newtcolorbox{reidai}[2]{%
 fonttitle = \gtfamily\sffamily\bfseries,
 colframe = ored,
 colback = white,
 enhanced,
 boxrule = 0.3mm,
 top=2pt,
 left=2pt,
 right=4pt,
 bottom=2pt,
 arc=0mm,
 title = 重要例題,
 titlerule = 0mm,
 after title=\hspace{4mm}{\AfterText{#1}{#2}},
 boxsep=0pt,
 right=0pt
}
\newcommand{\AfterText}[2]{%
\tcbox[%
 on line,
 boxsep=0pt,
 colframe = ored!20!white,
 colback = ored!20!white,
 boxrule=0.3mm,
 rightrule=0mm,
 top=0mm,bottom=0mm,
 left=2pt,
 sharp corners,
]
{%
\makebox[.849\textwidth][l]{\bfseries\gtfamily \thereidai\relax\hspace{2pt}| {#1} \hfill \ksfor{#2}\relax\strut}%
}}
\begin{document}
  \begin{reidai}{おき換えの利用}{4}
\begin{renumerate}
    \item 関数$y=x^{4}-6x^{2}+10$の最小値を求めよ。
\end{renumerate}
\end{reidai}

\end{document}

I have completed so far, but I want to make it like the attached picture. Please tell me how to make it. I would like to add a box with a shadow to the bottom of the red box that has been created so far, as shown in the attached photo.