# Part 6: FiniteNumberSets¶

It's possible to have finite number sets as solutions for certain questions of generic tex problems. The corresponding question type is "input.finite-number-set". Each answer of a question of that type has a finite number set as solution. The solution is specified by means of the `\solution`

command, as usual. The argument of the command must be a comma-separated list of variable names. Each variable denotes an element of the set. Of course, the variables must be defined somewhere in the problem. Please note: it is not possible to use literal numbers in the solution. You have to use variables.

Here is an example:

```
\usepackage{mumie.genericproblem}
\title{Scratch}
Test Test Test
\begin{problem}
\begin{question}
\begin{variables}
\number{a}{1/2}
\number{b}{1/3}
\number{c}{1/5}
\end{variables}
\text{\textit{Write down the set A of numbers $\var{a}$, $\var{b}$, and $\var{c}$}:}
\explanation{Test test Test}
\type{input.finite-number-set}
\field{rational}
\begin{answer}
\text{ A = }
\solution{a, b, c}
\end{answer}
\end{question}
\end{problem}
```

If the user has not edited the problem before, the problem applet of this example looks like the following:

The user has to click the button "Define set" to edit the set. Immediately after clicking the button an empty set shows up:

Elements can be added by means of the "+" button. The "-" button removes the last element:

Please note: The technique with the initial "Define set" button is needed to distinguish a not-edited set from an empty set. Initially, the set is not edited. Immediately after clicking the "Define set" buttun the set is considered edited, but empty.