CREATE TABLE table_37894 ("Call sign" TEXT, "Frequency MHz" FLOAT, "City of license" TEXT, "ERP W" FLOAT, "Class" TEXT, "FCC info" TEXT)

Which ERP W is the lowest one that has a Frequency MHz of 91.3?
SELECT MIN("ERP W") FROM table_37894 WHERE "Frequency MHz" = '91.3'
SELECT MIN("ERP W") FROM "table_37894" WHERE "Frequency MHz" = '91.3'