I would have to say to whom it may concern. Since it is showing correct vocabulary and directing it towards the person who ends up reading it.
Answer:
The answer is 50,000,000
Explanation:
Plague has been responsible for widespread pandemics with high mortality. It was known as the "Black Death" during the fourteenth century, causing an estimated 50 million deaths, approximately half of them in Asia and Africa and the other half in Europe, where a quarter of the population succumbed.
