I want to know the answer to the following question:
Which opera director did Frédéric see works of during his stay in Berlin?
All the background I'm provided with is that "In September 1828 Chopin, while still a student, visited Berlin with a family friend, zoologist Feliks Jarocki, enjoying operas directed by Gaspare Spontini and attending concerts by Carl Friedrich Zelter, Felix Mendelssohn and other celebrities.". Is that enough to answer the question?