what is the engine when the tyre is d, the constructor is era and the driver is bob gerard?
CREATE TABLE "entries" (
  "driver" text,
  "entrant" text,
  "constructor" text,
  "chassis" text,
  "engine" text,
  "tyre" text
);
SELECT "engine" FROM "entries" WHERE "tyre"='d' AND "constructor"='era' AND "driver"='bob gerard';