CREATE TABLE table_42409 ("City of license" TEXT, "Identifier" TEXT, "Frequency" TEXT, "Power" TEXT, "Class" TEXT, "RECNet" TEXT)

What is Class, when Power is 78 Watts?
SELECT "Class" FROM table_42409 WHERE "Power" = '78 watts'
SELECT "Class" FROM "table_42409" WHERE "Power" = '78 watts'