CREATE TABLE table_51993 ("Nation" TEXT, "Gold" FLOAT, "Silver" FLOAT, "Bronze" FLOAT, "Total" FLOAT)

What is the average amount of silver medals Montenegro, who has less than 15 bronze and more than 11 total medals, has?
SELECT AVG("Silver") FROM table_51993 WHERE "Bronze" < '15' AND "Nation" = 'montenegro' AND "Total" > '11'
SELECT AVG("Silver") FROM "table_51993" WHERE "Bronze" < '15' AND "Nation" = 'montenegro' AND "Total" > '11'