CREATE TABLE table_79685 ("Call sign" TEXT, "Frequency MHz" FLOAT, "City of license" TEXT, "ERP W" FLOAT, "Class" TEXT, "FCC info" TEXT)

What is the total frequency mhz of the kgrj call sign, which has an erp w greater than 21,500?
SELECT COUNT("Frequency MHz") FROM table_79685 WHERE "Call sign" = 'kgrj' AND "ERP W" > '21,500'
SELECT COUNT("Frequency MHz") FROM "table_79685" WHERE "Call sign" = 'kgrj' AND "ERP W" > '21,500'