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 | Country | Project | Status at production | Original air date |
| --- | --- | --- | --- | --- | --- | --- |
| 70.0 | 1.0 | "Rebuilding New York City's Subway" | United States | New York City subway expansion | Under construction | April8,2011 |
| 71.0 | 2.0 | "Drought-Proofing Australia" | Australia | Wonthaggi desalination plant | Under construction | April15,2011 |
| 72.0 | 3.0 | "Azerbaijan's Amazing Transformation" | Azerbaijan | Flame Towers and Heydar Aliyev Cultural Centre | Under construction | April22,2011 |
| 73.0 | 4.0 | "London's Olympic Aquatic Stadium" | United Kingdom | London Aquatics Centre | Under construction | April29,2011 |
| 74.0 | 5.0 | "Constructing Serbia's Largest Bridge" | Serbia | Ada Bridge | Under construction | June18,2011 |
| 75.0 | 6.0 | "Amsterdam's Futuristic Floating City" | Netherlands | Netherlands land expansion | Under construction | June25,2011 |
| 76.0 | 7.0 | "Building Mumbai 's Modern Airport" | India | Chhatrapati Shivaji International Airport | Under construction | July2,2011 |
Question:
What was the original are date of series number 71?
Answer:
April15,2011