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:
| No. in series | No. in season | Title | Directed by | Written by | Original air date | Production code(s) | U.S. viewers (millions) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 122.0 | 1.0 | " The One After Vegas " | Kevin S. Bright | Adam Chase | September23,1999 | 225551.0 | 27.7 |
| 123.0 | 2.0 | "The One Where Ross Hugs Rachel" | Gail Mancuso | Shana Goldberg-Meehan | September30,1999 | 225552.0 | 22.9 |
| 124.0 | 3.0 | "The One with Ross's Denial" | Gary Halvorson | Seth Kurland | October7,1999 | 225553.0 | 21.6 |
| 125.0 | 4.0 | "The One Where Joey Loses His Insurance" | Gary Halvorson | Andrew Reich & Ted Cohen | October14,1999 | 225554.0 | 21.1 |
| 126.0 | 5.0 | "The One with Joey's Porsche" | Gary Halvorson | Perry Rein & Gigi McCreery | October21,1999 | 225555.0 | 22.4 |
| 127.0 | 6.0 | "The One on the Last Night" | David Schwimmer | Scott Silveri | November4,1999 | 225556.0 | 23.6 |
| 128.0 | 7.0 | "The One Where Phoebe Runs" | Gary Halvorson | Sherry Bilsing-Graham & Ellen Plummer | November11,1999 | 225557.0 | 22.7 |
| 130.0 | 9.0 | "The One Where Ross Got High" | Kevin S. Bright | Gregory S. Malins | November25,1999 | 225559.0 | 19.2 |
| 132.0 | 11.0 | " The One with the Apothecary Table " | Kevin S. Bright | Story: Zachary Rosenblatt Teleplay: Brian Boyle | January6,2000 | 225560.0 | 22.3 |
| 135.0 | 14.0 | "The One Where Chandler Can't Cry" | Kevin S. Bright | Andrew Reich & Ted Cohen | February10,2000 | 225564.0 | 23.8 |
| 138.0 | 17.0 | "The One with Unagi" "The One with the Mix Tape" | Gary Halvorson | Story: Zachary Rosenblatt Teleplay: Adam Chase | February24,2000 | 225568.0 | 22.1 |
| 139.0 | 18.0 | "The One Where Ross Dates a Student" | Gary Halvorson | Seth Kurland | March9,2000 | 225567.0 | 20.5 |
| 141.0 | 20.0 | "The One with Mac and C.H.E.E.S.E." | Kevin S. Bright | Doty Abrams | April13,2000 | 225575.0 | 18.8 |
| 142.0 | 21.0 | "The One Where Ross Meets Elizabeth's Dad" | Michael Lembeck | Story: David J. Lagana Teleplay: Scott Silveri | April27,2000 | 225570.0 | 20.6 |
Question:
who are the directors of the episode that had 20.5 millions of north american viewers? 
Answer:
Gary Halvorson