CREATE TABLE table_71455 ("Call sign" TEXT, "Frequency MHz" FLOAT, "City of license" TEXT, "ERP W" FLOAT, "Class" TEXT, "FCC info" TEXT)

what is the highest frequency mhz with the call sign w292cu?
SELECT MAX("Frequency MHz") FROM table_71455 WHERE "Call sign" = 'w292cu'
SELECT MAX("Frequency MHz") FROM "table_71455" WHERE "Call sign" = 'w292cu'