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 airdate | U.S. viewers (millions) |
| --- | --- | --- | --- | --- | --- | --- |
| 71.0 | 1.0 | "Shalom" | William Webb | Donald P. Bellisario and John Kelley | September19,2006 | 13.80 |
| 72.0 | 2.0 | "Escaped" | Dennis Smith | Steven D. Binder and Christopher Silber | September26,2006 | 14.12 |
| 73.0 | 3.0 | "Singled Out" | Terrence O'Hara | David North | October3,2006 | 15.89 |
| 74.0 | 4.0 | "Faking It" | Thomas J. Wright | Shane Brennan | October10,2006 | 15.86 |
| 75.0 | 5.0 | "Dead and Unburied" | Colin Bucksey | Nell Scovell | October17,2006 | 15.92 |
| 76.0 | 6.0 | "Witch Hunt" | James Whitmore, Jr. | Steven Kriozere | October31,2006 | 15.94 |
| 77.0 | 7.0 | "Sandblast" | Dennis Smith | Robert Palm | November7,2006 | 15.44 |
| 78.0 | 8.0 | "Once a Hero" | Thomas J. Wright | Shane Brennan | November14,2006 | 15.80 |
| 79.0 | 9.0 | "Twisted Sister" | Terrence O'Hara | Steven D. Binder | November21,2006 | 17.00 |
| 80.0 | 10.0 | "Smoked" | Dennis Smith | John Kelley and Robert Palm | November28,2006 | 17.96 |
| 81.0 | 11.0 | "Driven" | Dennis Smith | Richard Arthur, John Kelley and Nell Scovell | December12,2006 | 17.39 |
| 82.0 | 12.0 | "Suspicion" | Colin Bucksey | Shane Brennan | January16,2007 | 15.95 |
| 83.0 | 13.0 | "Sharif Returns" | Terrence O'Hara | Steven D. Binder | January23,2007 | 14.83 |
| 84.0 | 14.0 | "Blowback" | Thomas J. Wright | Shane Brennan, David North and Christopher Silber | February6,2007 | 16.16 |
| 85.0 | 15.0 | "Friends and Lovers" | Dennis Smith | John Kelley | February13,2007 | 15.36 |
| 86.0 | 16.0 | "Dead Man Walking" | Colin Bucksey | Nell Scovell | February20,2007 | 15.90 |
| 87.0 | 17.0 | "Skeletons" | James Whitmore, Jr. | Jesse Stern | February27,2007 | 16.16 |
| 88.0 | 18.0 | "Iceman" | Thomas J. Wright | Shane Brennan | March20,2007 | 15.69 |
| 89.0 | 19.0 | " Grace Period " | James Whitmore, Jr. | John Kelley | April3,2007 | 13.79 |
| 90.0 | 20.0 | "Cover Story" | Dennis Smith | David North | April10,2007 | 14.38 |
| 91.0 | 21.0 | "Brothers in Arms" | Martha Mitchell | Steven D. Binder | April24,2007 | 14.17 |
| 92.0 | 22.0 | "In the Dark" | Thomas J. Wright | Steven D. Binder | May1,2007 | 13.83 |
| 93.0 | 23.0 | "Trojan Horse" | Terrence O'Hara | Shane Brennan and Donald Bellisario | May8,2007 | 13.88 |
Question:
How many millions of U.S. viewers watched the episode titled "Once a Hero"?
Answer:
15.8