SELECT m.MOD_NAME AS ModelName,
    a.AC_TTAF AS TotalHours,
    a.AC_TTEL AS TotalHrsLeftEngine,
    a.AC_TTER AS TotalHrsRightEngine,
    (100 - (a.AC_TTAF MOD 100)) AS HrsToExam,
    (40 - (a.AC_TTEL MOD 40)) AS HrsToService_Left,
    (40 - (a.AC_TTER MOD 40)) AS HrsToService_Right
FROM aircraft a, model m
WHERE a.AC_NUMBER = aircraft_number
AND m.MOD_CODE = a.MOD_CODE