Which Frequency MHz has an ERP W larger than 4, and a Call sign of w218ap?
CREATE TABLE "repeaters" (
  "call_sign" text,
  "frequency_m_hz" text,
  "city_of_license" text,
  "erp_w" real,
  "fcc_info" text
);
SELECT "frequency_m_hz" FROM "repeaters" WHERE "erp_w">4 AND "call_sign"='w218ap';