CREATE TABLE table_21998 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Country" TEXT, "Project" TEXT, "Status at production" TEXT, "Original air date" TEXT)

What series number was the 'rebuilding new york city's subway' project?
SELECT MIN("No. in series") FROM table_21998 WHERE "Title" = 'Rebuilding New York City''s Subway'
SELECT MIN("No. in series") FROM "table_21998" WHERE "Title" = 'Rebuilding New York City\'s Subway'