Method does not exist or incorrect signature: [BusinessHours].diff(Id, Time, Time)

BusinessHours bh = [SELECT FridayEndTime,FridayStartTime,Id,IsActive,IsDefault,LastModifiedById,
                              LastModifiedDate,MondayEndTime,MondayStartTime,Name,SaturdayEndTime,
                              SaturdayStartTime,SundayEndTime,SundayStartTime,SystemModstamp,ThursdayEndTime,
                              ThursdayStartTime,TimeZoneSidKey,TuesdayEndTime,TuesdayStartTime,
                              WednesdayEndTime,WednesdayStartTime FROM BusinessHours where Name='XXX Hours'
                               LIMIT 1];
        Datetime dt = bh.diff(bh.Id, bh.MondayStartTime, bh.MondayEndTime);