Modify the program from the case study to remove records from the data file. Define functi...

Modify the program from the case study to remove records from the data file. Define function isNull() in classes Personal and Student to determine that a record is null. Define function writeNullToFile() in the two classes to overwrite a record to be deleted by a null record. A null record can be defined as having a nonnumeric character (a tombstone) in the first position of the SSN member. Then define function remove() in Database (very similar to modify()), which locates the position of a record to be deleted and overwrites it with the null record. After a session is finished, a Database destructor should be invoked, which copies nonnull records to a new data file, deletes the old data file, and renames the new data file with the name of the old data file