user: Question: What is the average year to begin making autos for a brand that joined GM in 1917?
Columns: ['Brand', 'Year founded', 'Year began making autos', 'Year joined GM', 'Markets served today']
Types: ['text', 'real', 'real', 'real', 'text']
Sample row: ['Baojun', 2010.0, 2010.0, 2010.0, 'China']
SQL:

assistant: SELECT AVG("Year began making autos") FROM "Table" WHERE "Year joined GM" = 1917.0;