user: Question: What is the average goals when the last appearance was before 1984, there were more than 17 appearances, the first appearance was before 1961 and the position was MF?
Columns: ['Position', 'Appearances', 'Goals', 'First appearance', 'Last appearance']
Types: ['text', 'real', 'real', 'real', 'real']
Sample row: ['GK', 1.0, 0.0, 1990.0, 1990.0]
SQL:

assistant: SELECT AVG("Goals") FROM "Table" WHERE "Last appearance" < 1984.0 AND "Appearances" > 17.0 AND "First appearance" < 1961.0 AND "Position" = 'MF';