What is the Interregnum ended for Count Palatine of Saxony of frederick augustus i, elector of saxony?
CREATE TABLE "list_of_imperial_vicars_1437_1792" (
  "interregnum_began" text,
  "interregnum_ended" text,
  "duration" text,
  "count_palatine_of_saxony" text,
  "count_palatine_of_the_rhine" text
);
SELECT "interregnum_ended" FROM "list_of_imperial_vicars_1437_1792" WHERE "count_palatine_of_saxony"='frederick augustus i, elector of saxony';