CREATE TABLE table_71969 ("Call sign" TEXT, "Frequency" TEXT, "City of license" TEXT, "Facility ID" FLOAT, "ERP / Power W" FLOAT, "Height m  (  ft  ) " TEXT, "Class" TEXT)

Name the frequency with class of b
SELECT "Frequency" FROM table_71969 WHERE "Class" = 'b'
SELECT "Frequency" FROM "table_71969" WHERE "Class" = 'b'