What is the ERP W number where the frequency is smaller than 91.1?
CREATE TABLE "broadcast_translators_of_whrz_lp" (
  "call_sign" text,
  "frequency_m_hz" real,
  "city_of_license" text,
  "erp_w" real,
  "class" text,
  "fcc_info" text
);
SELECT MAX("erp_w") FROM "broadcast_translators_of_whrz_lp" WHERE "frequency_m_hz"<91.1;