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:
| Rank | City 1 | City 2 | 2012 Passengers (in millions) | 2011 Passengers (in millions) | Distance |
| --- | --- | --- | --- | --- | --- |
| 1.0 | Seoul | Jeju | 10.156 | 9.9 | 450km |
| 2.0 | Tokyo | Sapporo | 8.211 | 7.5 | 819km |
| 3.0 | São Paulo | Rio de Janeiro | 7.716 | 7.6+ | 366km |
| 4.0 | Beijing | Shanghai | 7.246 | 6.6+ | 1075km |
| 5.0 | Sydney | Melbourne | 6.943 | 7.0+ | 706km |
| 6.0 | Tokyo | Osaka | 6.744 | 7.5 | 405km |
| 7.0 | Tokyo | Fukuoka | 6.640 | 6.6+ | 883km |
| 8.0 | Hong Kong | Taipei | 5.513 | 6.2+ | 780km |
| 9.0 | Tokyo | Okinawa | 4.584 | 4.1 | 1554km |
Question:
How many passengers (in millions) in 2011 flew through along the route that had 6.640 million passengers in 2012?
Answer:
6.6+