CREATE TABLE table_72141 ("No. in season" FLOAT, "No. in series" FLOAT, "Title" TEXT, "Canadian airdate" TEXT, "US airdate" TEXT, "Production code" FLOAT)

The canadian airdate of 17 march 2008 had how many numbers in the season?
SELECT COUNT("No. in season") FROM table_72141 WHERE "Canadian airdate" = '17 March 2008'
SELECT COUNT("No. in season") FROM "table_72141" WHERE "Canadian airdate" = '17 March 2008'