What is the average grid that has a Constructor of brm, tony maggs, and a Laps larger than 102?
CREATE TABLE "classification" (
  "driver" text,
  "constructor" text,
  "laps" real,
  "time_retired" text,
  "grid" real
);
SELECT AVG("grid") FROM "classification" WHERE "constructor"='brm' AND "driver"='tony maggs' AND "laps">102;