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:
| Series # | Title | Directed by | Written by | France air date | Canadian air date | US air date |
| --- | --- | --- | --- | --- | --- | --- |
| 1.0 | "Pilot" "Pilote" | John Stead & Duane Clark | Gil Grant | 18April2011 | 19 April 2011 | 29 June 2012 |
| 2.0 | "Green Falls" "Green Falls" | Philippe Haïm | Philippe Lyon | 18April2011 | 26 April 2011 | 6 July 2012 |
| 3.0 | "Lockdown" "Sans issue" | Duane Clark | Charles Heit | 25April2011 | 3 May 2011 | 13 July 2012 |
| 4.0 | "The Irish Version" "La Version irlandaise" | Xavier Palud | Denis McGrath | 25April2011 | 10 May 2011 | 20 July 2012 |
| 5.0 | "Training Camp" "Bienvenue à Bitterroot" | Duane Clark | Pamela Davis | 2May2011 | 17 May 2011 | 27 July 2012 |
| 6.0 | "Costa Verde" "Opération Costa Verde" | Michael Robison | Peter Mohan | 2May2011 | 25 May 2011 | 17 August 2012 |
| 7.0 | "Undertow" "Plongée en eaux troubles" | Paul Shapiro | Andrea Stevens | 9May2011 | 1 June 2011 | 24 August 2012 |
| 8.0 | "Hunting Party" "Une partie de chasse" | Alain Tasma | Grant Rosenberg | 9May2011 | 8 June 2011 | 31 August 2012 |
| 9.0 | "The Bank Job" "Braquage à la russe" | Lee Rose | Denis McGrath | 16May2011 | 15 June 2011 | 7 September 2012 |
| 10.0 | "The Train" "L'enlèvement" | Steve DiMarco | Charles Heit | 16May2011 | 22 June 2011 | 14 September 2012 |
| 11.0 | "The Bunker" "Le Bunker" | Ken Girotti | Peter Mohan | 23May2011 | 30 June 2011 | 21 September 2012 |
| 12.0 | "The Key" "La Clé" | Alain Tasma | Grant Rosenberg | 23May2011 | 5 July 2011 | 28 September 2012 |
Question:
What is the US air date when the director is ken girotti?
Answer:
21 September 2012