Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| State (class) | Vacator | Reason for change | Successor | Date of successors formal installation |
| --- | --- | --- | --- | --- |
| Alabama (2) | New seats | Alabama was admitted to the Union. | John W. Walker (DR) | Elected December 14, 1819 |
| Alabama (3) | New seats | Alabama was admitted to the Union. | William R. King (DR) | Elected December 14, 1819 |
| Maine (2) | New seats | Maine was admitted to the Union. | John Holmes (F) | Elected June 13, 1820 |
| Maine (1) | New seats | Maine was admitted to the Union. | John Chandler (DR) | Elected June 14, 1820 |
| Maryland (1) | Alexander C. Hanson (F) | Died April 23, 1819 | William Pinkney (DR) | Elected December 21, 1819 |
| Virginia (2) | John W. Eppes (DR) | Resigned December 4, 1819 | James Pleasants (DR) | Elected December 10, 1819 |
| Massachusetts (1) | Prentiss Mellen (F) | Resigned May 15, 1820 | Elijah H. Mills (F) | Elected June 12, 1820 |
| Rhode Island (2) | James Burrill, Jr. (F) | Died December 25, 1820 | Nehemiah R. Knight (DR) | Elected January 9, 1821 |
Question:
what is the state for reason for change is resigned may 15, 1820?
Answer:
Massachusetts (1)