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 | Main colour(s) | Additional colour(s) | Livery | Additional major sponsor(s) |
| --- | --- | --- | --- | --- |
| 1978.0 | Yellow | Black | ATS Wheels | Ford, Champion, Air Press, Shell, Goodyear |
| 1979.0 | Yellow | Black, Red | ATS Wheels, Arawak, Hotel Freeport | Goodyear, Shell |
| 1980.0 | Yellow | Black, Red | ATS Wheels, Arawak, Hotel Freeport | Shell, Buler Quartz, Goodyear |
| 1981.0 | Yellow | White, Black | ATS Wheels | ABBA , Shell, Champion |
| 1981.0 | Yellow | White, Black | ATS Wheels | Copec, Tecfin, Liqui Moly, Shell, Champion |
| 1983.0 | Yellow | Black | ATS Wheels | Shell, Goodyear, Steinbock |
| 1984.0 | Yellow | Black | ATS Wheels | Marilena, Steinbock, Shell, Pirelli |
Question:
What is the average year of entries with additional color black?
Answer:
1981.6666666666667