What is the sum of all the points won by Peter Whitehead in an alta f2 Chassis?
CREATE TABLE "complete_world_championship_results" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" real
);
SELECT SUM("points") FROM "complete_world_championship_results" WHERE "entrant"='peter whitehead' AND "chassis"='alta f2';