Ошибка: "Ссылка на неразрешенный внешний символ MenuSelection" - C (СИ)

#include<stdio.h>
#include"metr.h"
  main()
{
  int quitting = FALSE;
  printf("Welcom to Metrics \n");
  while (!quitting)
    {
        DisplayMenu();
        switch(MenuSelection())
        {
        case 1:
            InchestoCentimeters();break;
        case 9:
            quitting = TRUE;
        }
  }
  return 0;
}
void DisplayMenu(void)
{
  printf("Menu\n");
  printf("-------\n");
  printf("1 - Inches to Centimeters\n");
  printf("2- Centimeters to Inches\n");
  printf("3 - Feet to meters\n");
  printf("4 - meters to Feet\n");
  printf("5 - Miles to kilometrs\n");
  printf("6 - kilometrs to miles\n");
  printf("9 - quin\n");
}
 double GetValue(void)
 {
   double value;
    printf("\nValue to convert?\n");
    scanf ("%lf", &value);
    return value;
 }
  void InchestoCentimeters(void)
  {
    double value;
    double result;
    printf("Inches to Centimeters\n");
    value = GetValue();
    result = value * CENT_PER_INCH;
    printf("%.3lf inches = %.3lf cents\n", value,result);
  }

#include<conio.h>
#define FALSE 0
#define TRUE 1
#define CENT_PER_INCH 2.54;
 
void DisplayMenu(void);
int MenuSelection(void);
double GetValue(void);
void InchestoCentimeters(void);