Totcount depending on environment

Question

I'd like to have a counter, called ProblemPoints in the MWE, which is dependent on an environment problem, such that I can print the total points of each problem.

\documentclass{article}
\usepackage{totcount}
\newtotcounter{ProblemPoints}

\newenvironment{problem}
{
\setcounter{ProblemPoints}{0}
Problem: (\total{ProblemPoints} points)
}
{\vspace{1cm}}

\begin{document}
\begin{problem}
Question 1: (2 points)\addtocounter{ProblemPoints}{2}
Question 2: (2 points)\addtocounter{ProblemPoints}{2}
\end{problem}
\begin{problem}
Question 1: (5 points)\addtocounter{ProblemPoints}{5}
Question 2: (1 points)\addtocounter{ProblemPoints}{1}
\end{problem}
\end{document}

Here it just prints 6 (the total points of the last Problem) at each problem.

Answer 1

\total can only store one value. You can use the \label-\ref method.

\documentclass{article}

\newcounter{problem}
\newcounter{problempoints}
\renewcommand{\theproblem}{\theproblempoints}
\newcounter{question}

\newenvironment{problem}
 {%
  \par\addvspace{1cm}%
  \stepcounter{problem}%
  \setcounter{question}{0}%
  \setcounter{problempoints}{0}%
  Problem: (\ref{PB\arabic{problem}} points)\par
 }
 {%
  \addtocounter{problem}{-1}%
  \refstepcounter{problem}\label{PB\arabic{problem}}%
  \par\addvspace{1cm}%
 }
\newcommand{\question}[1]{%
  \par
  \stepcounter{question}%
  Question \thequestion: (#1 points)\addtocounter{problempoints}{#1}
}

\begin{document}
\begin{problem}
\question{2} What is $1+2$?
\question{2} What is $1+3$?
\end{problem}
\begin{problem}
\question{5} What is $100\cdot 100$?
\question{1} What is $2^4-4^2$?
\end{problem}
\end{document}

Each problem steps a counter for getting a label expanding to the final value of \theproblempoints.

I do \stepcounter at the beginning, then step back the counter and do \refstepcounter again, in order to set the current label at the last minute, so you can also use \label inside the environment.