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:
| Year | Chassis | Engine | Start | Finish |
| --- | --- | --- | --- | --- |
| 1974 | Eagle | Offy | 21st | 7th |
| 1975 | Eagle | Offy | 18th | 4th |
| 1976 | Eagle | Offy | 6th | 5th |
| 1977 | Eagle | Offy | 8th | 15th |
| 1978 | Lighning | Cosworth | 21st | 24th |
| 1979 | Lighning | Cosworth | 17th | 20th |
| 1980 | Penske | Cosworth | 8th | 6th |
| 1981 | Penske | Cosworth | 10th | 28th |
| 1982 | March | Cosworth | 10th | 3rd |
| 1983 | March | Cosworth | 14th | 7th |
| 1984 | March | Cosworth | 21st | 19th |
| 1985 | March | Buick | 1st | 33rd |
| 1986 | Lola | Cosworth | 14th | 16th |
| 1987 | March | Cosworth | 29th | 27th |
| 1988 | March | Buick | Qualifying Crash |  |
| 1989 | Lola | Cosworth | 32nd | 22nd |
| 1990 | Lola | Cosworth | 22nd | 29th |
| 1991 | Lola | Buick | 32nd | 21st |
| 1992 | Lola | Buick | Failed to Qualify |  |
| 1994 | Lola | Chevrolet | Failed to Qualify |  |
Question:
what is the average engine type listed?
Answer:
Cosworth