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:
| Manufacturer | Model | Quantity | Introduced | Retired |
| --- | --- | --- | --- | --- |
| Douglas | C-54 Skymaster | 6.0 | 1947.0 | 1966.0 |
| Douglas | C-47 Dakota | 2.0 | 1947.0 | 1964.0 |
| de Havilland | DH.114 Heron | 7.0 | 1952.0 | 1960.0 |
| Fokker | F-27 Friendship | 8.0 | 1958.0 | 1977.0 |
| Douglas | DC-6A/C | 1.0 | 1961.0 | 1965.0 |
| Douglas | DC-6B | 7.0 | 1962.0 | 1973.0 |
| Fokker | F-28 Fellowship | 6.0 | 1969.0 | 1986.0 |
| Boeing | 737-200 | 20.0 | 1969.0 | 1994.0 |
| Boeing | 767-200 | 2.0 | 1984.0 | 1986.0 |
| Boeing | 737-400 | 7.0 | 1989.0 | 2004.0 |
| Boeing | 737-500 | 17.0 | 1990.0 | 2004.0 |
| Fokker | 100 | 5.0 | 1997.0 | 1999.0 |
| Boeing | 737-300 | 1.0 | 1997.0 | 1999.0 |
| Boeing | 737-700 | 13.0 | 1998.0 | 2004.0 |
| British Aerospace | 146–200 | 10.0 | 1998.0 | 2001.0 |
Question:
What is the total number of quantity when the introductory year was 1984?
Answer:
2.0