The Vec destructor should:
Technically, only the first step is strictly necessary.
The reason is that the destructor is only invoked at the end of an object's lifetime.
Since the object will no longer exist, resetting its instance variables is not necessary
(except to pass the test).
- Use delete  to deallocate the array whose addres is stored in myArray;
- Set myArray to NULL; and
- Set mySize to zero.