CREATE TABLE table_21854 ("Episode" FLOAT, "Original title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original airdate" CLOB, "Duration" CLOB, "Viewership" CLOB)

How many episodes of 30 minutes were written by John Sullivan?
SELECT COUNT("Duration") FROM table_21854 WHERE "Written by" = 'John Sullivan'
SELECT COUNT("Duration") FROM "table_21854" WHERE "Written by" = 'John Sullivan'