Table: public_sector_companies
Columns: s_no
company
incorporated
ministry
sector

Question: What is the sector of the company with an incorporated date before 1983?
SQL: SELECT "sector" FROM public_sector_companies WHERE "incorporated" < 1983

Question: What is the average incorporataed year of the Air India Charters company?
SQL: SELECT AVG("incorporated") FROM public_sector_companies WHERE "company" = 'air india charters'