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 | Song title | Composer(s) | Performer(s) | Year |
| --- | --- | --- | --- | --- |
| 1.0 | " All I Want for Christmas Is You " | Mariah Carey and Walter Afanasieff | Mariah Carey | 1994.0 |
| 2.0 | " Last Christmas " | George Michael | Wham! | 1984.0 |
| 3.0 | " Fairytale of New York " | Jem Finer and Shane MacGowan | The Pogues with Kirsty MacColl | 1987.0 |
| 4.0 | " Do They Know It’s Christmas? " | Bob Geldof and Midge Ure | Band Aid | 1984.0 |
| 5.0 | " Merry Xmas Everybody " | Noddy Holder and Jim Lea | Slade | 1973.0 |
| 6.0 | " White Christmas " | Irving Berlin | Louis Armstrong | 1940.0 |
| 7.0 | " Driving Home for Christmas " | Chris Rea | Chris Rea | 1988.0 |
| 8.0 | " Merry Christmas Everyone " | Bob Heatlie | Shakin' Stevens | 1985.0 |
| 9.0 | " Mistletoe and Wine " | Jeremy Paul, Leslie Stewart and Keith Strachan | Cliff Richard | 1976.0 |
| 10.0 | " Walking in the Air " | Howard Blake | Peter Auty | 1982.0 |
Question:
How many years was Louis Armstrong performing?
Answer:
1.0