Ошибка LNK2001 неразрешенный внешний символ ""public: static int Question::count" (?count@Question@@2HA)"?

#include<iostream>
#include<string>
#include<fstream>
using namespace std;


class Question {

public:

    static void setCount();



private:
    string qestion;
    string answer1;
    string answer2;
    string answer3;
    string answer4;
    short int correct_answer;
    static int count;
};

void Question::setCount()
{
    fstream file;
    try
    {
        file.open("info.txt", fstream::in);
        int a;
        file >> a;
        Question::count = a;
        cout << a << endl;
    }
    catch (const fstream::failure& fail)
    {
        cout << fail.what() << endl << fail.code() << endl;
    }
}