the correct answer is D.13750 but i need to know to find the answer. thanks!

33. Blackhawk Company purchased a copyright for a book for $50,000 with a remaining legal life of 20 years and paid $5,000 in legal fees in the purchase. Blackhawk spent $6,000 on advertising for the new book and expects the book to generate profits for 4 years. The amortization of the copyright would be: A. $2,500 D. $13,750 B. $2,750 E. $15,250 C. $12,500