What is the yield in NTS Area U2R when the purpose is weapons development?
CREATE TABLE "flintlock_tests" (
  "name" text,
  "location" text,
  "elevation_height" text,
  "delivery" text,
  "purpose" text,
  "yield" text
);
SELECT "yield" FROM "flintlock_tests" WHERE "purpose"='weapons development' AND "location"='nts area u2r';