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 no. | Season no. | Title | Directed by | Written by | Original air date | Production code | U.S. viewers (millions) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 32.0 | 1.0 | "The Boy with the Pancakes Tattoo" | Lake Bell | Ken Marino & Erica Oyama | August 10, 2012 | 411.0 | 1.64 |
| 33.0 | 2.0 | "Staff Dance" | Steve Pink | Jonathan Stern | August17,2012 | 409.0 | 1.73 |
| 34.0 | 3.0 | "Chief's Origin" | Steve Pink | Rob Corddry | August24,2012 | 410.0 | 1.68 |
| 35.0 | 4.0 | "Free Day" | Rob Schrab | Ken Marino & Erica Oyama | August31,2012 | 401.0 | 1.57 |
| 36.0 | 5.0 | "Behind the Scenes" | Michael Patrick Jann | David Wain | September7,2012 | 406.0 | N/A |
| 37.0 | 6.0 | "The Return of the Young Billionaire" | Rob Schrab | Rob Huebel | September14,2012 | 402.0 | 1.61 |
| 38.0 | 7.0 | "British Hospital" | Tristram Shapeero | Sam Bain | September21,2012 | 408.0 | 1.44 |
| 39.0 | 8.0 | "Ladies Night" | David Wain | Ken Marino & Erica Oyama | September28,2012 | 403.0 | 1.42 |
| 40.0 | 9.0 | "A Kid Walks in to a Hospital" | Lake Bell | Rob Corddry & Jonathan Stern | October5,2012 | 412.0 | 1.35 |
| 41.0 | 10.0 | "A Year in the Life" | David Wain | David Wain | October19,2012 | 404.0 | 1.55 |
| 42.0 | 11.0 | "Attention Staff" | Ken Marino | Rob Corddry | October26,2012 | 413.0 | 1.45 |
| 43.0 | 12.0 | "Childrens Lawspital" | Ken Marino | Jason Mantzoukas | November2,2012 | 414.0 | 1.68 |
| 44.0 | 13.0 | "Wisedocs" | Michael Patrick Jann | Rob Corddry | November9,2012 | 407.0 | N/A |
Question:
When was originally aired the episode with an audience of 1.57 million us viewers?
Answer:
August31,2012