CREATE TABLE table_name_17 (year INT, engine VARCHAR, entrant VARCHAR)

What is the average Year when there was a cosworth straight-4 engine, and the Entrant was ron harris / team lotus?
SELECT AVG(year) FROM table_name_17 WHERE engine = "cosworth straight-4" AND entrant = "ron harris / team lotus"
SELECT AVG("year") FROM "table_name_17" WHERE "cosworth straight-4" = "engine" AND "entrant" = "ron harris / team lotus"