This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
In a certain population, there were 4050 births in the last one year. There were 50 still births. 50 infants died within 7 days whereas 150 died within the first 28 days. What is the neonatal mortality rate? 
Select and explain. 
A. 62.5, B. 50, C. 12.5, D. 49.4
B: 50
Answer: B: 50 
Explanation: None