Which specific dates encompass the time period when "The Show Girl Must Go On" showed a gross sales figure total of $2,877,906?
CREATE TABLE "table1_22123920_4" (
  "dates_mdy" text,
  "gross_sales" text,
  "tickets_sold_available" text,
  "shows_sellout" text,
  "sellout_pct" text
);
SELECT "dates_mdy" FROM "table1_22123920_4" WHERE "gross_sales"='$2,877,906';