# How to input an endmark in an environment different from the proof environment?

I want to put an endmark in the solution environment, I tried

\documentclass{article}
\usepackage{amsthm}
\usepackage{amssymb,amsmath}
\newtheorem{mytheorem}{Theorem}[section]
\newtheorem{ex}{Example}[section]
\begin{document}
\section{Section one}
\begin{mytheorem}
If $$U$$ or $$V$$ then...

\begin{proof}[Proof]
The Proof
\begin{equation*}
Ax = b.
\end{equation*}
\end{proof}
\end{mytheorem}

\begin{ex}
This is a example
\end{ex}
\begin{proof}[Solution]
\renewcommand{\qedsymbol}{\ensuremath{\diamondsuit}}
This is a solution
\end{proof}
\end{document}


How do I write a command in the preamble to put an endmark in the solution environment?

-

\newenvironment{mysol}{%

Then you just write your solutions with the environment mysol.