Which Performance has a Usage of hepa and a Class of h14?
CREATE TABLE "filter_classes" (
  "usage" text,
  "class" text,
  "performance" text,
  "performance_test" text,
  "particulate_size_approaching_100pct_retention" text,
  "test_standard" text
);
SELECT "performance" FROM "filter_classes" WHERE "usage"='hepa' AND "class"='h14';