//file1.h#define USD 1

//file2.h#define UKP 1

//file3
#include <stdio.h>
#include <file1.h>               //A#if !defined (USD) || !defined (UKP)      // B#error “ERROR: NO_CURRENCY rate is specified.”  //C#endif

 main()
{        
    int rs;
    rs = 10 * currency_rate;          //D
    printf (“%d\n”, rs);
}