CREATE TABLE table_name_19 (silver INT, nation VARCHAR, total VARCHAR, rank VARCHAR)

What is the sum of Silver when the total is less than 6, the rank is 6 and the Bulgaria is the nation?
SELECT SUM(silver) FROM table_name_19 WHERE total < "6" AND rank = "6" AND nation = "bulgaria"
SELECT SUM("silver") FROM "table_name_19" WHERE "6" = "rank" AND "6" > "total" AND "bulgaria" = "nation"