CREATE TABLE table_15716 ("Year" FLOAT, "Entrant" CLOB, "Chassis" CLOB, "Engine" CLOB, "Points" FLOAT)

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_15716 WHERE "Engine" = 'cosworth straight-4' AND "Entrant" = 'ron harris / team lotus'
SELECT AVG("Year") FROM "table_15716" WHERE "Engine" = 'cosworth straight-4' AND "Entrant" = 'ron harris / team lotus'