How many chapters have the name Gratiano as a character for "friend to Antonio and Bassiano"?
name Gratiano as a character refers to CharName = 'Gratiano'; "friend to Antonio and Bassiano" refers to characters.Description = 'friend to Antonio and Bassiano'
SELECT COUNT(DISTINCT T2.chapter_id) FROM characters AS T1 INNER JOIN paragraphs AS T2 ON T1.id = T2.character_id WHERE T1.CharName = 'Gratiano' AND T1.Description = 'friend to Antonio and Bassiano'