CREATE TABLE table_204_864 (id DECIMAL, "pos" DECIMAL, "class" TEXT, "no" DECIMAL, "team" TEXT, "drivers" TEXT, "chassis" TEXT, "engine" TEXT)

how many times did franz race with his simca 2.0 l engine ?
SELECT COUNT(*) FROM table_204_864 WHERE "drivers" = 'franz hummel' AND "engine" = 'roc-simca 2.0l i4'
SELECT COUNT(*) FROM "table_204_864" WHERE "drivers" = 'franz hummel' AND "engine" = 'roc-simca 2.0l i4'