Question: As a result of the Black Death, how much was the population reduced in the place that the US helped with the Marshall Plan?

Knowledge 1: Marshall Plan
The Marshall Plan (officially the European Recovery Program, ERP) was an American initiative to aid Western Europe, in which the United States gave over $12 billion (nearly $100 billion in 2016 US dollars) in economic assistance to help rebuild Western European economies after the end of World War II. The plan was in operation for four years beginning on April 3, 1948. The goals of the United States were to rebuild war - torn regions, remove trade barriers, modernize industry, improve European prosperity, and prevent the spread of Communism. The Marshall Plan required a lessening of interstate barriers, a dropping of many regulations, and encouraged an increase in productivity, trade union membership, as well as the adoption of modern business procedures. [SEP] Knowledge 2: Consequences of the Black Death
Consequences of the Black Death included a series of religious, social, and economic upheavals, which had profound effects on the course of European history. The Black Death was one of the most devastating pandemics in human history, peaking in Europe between 1347 and 1350 with 30% to 65% of the population killed. It reduced world population from an estimated 450 million to between 350 and 375 million. It took 80 and in some areas more than 150 years for Europe's population to recover.
Knowledge 1: Marshall Plan
The Marshall Plan (officially the European Recovery Program, ERP) was an American initiative to aid Western Europe, in which the United States gave over $12 billion (nearly $100 billion in 2016 US dollars) in economic assistance to help rebuild Western European economies after the end of World War II. The plan was in operation for four years beginning on April 3, 1948. The goals of the United States were to rebuild war - torn regions, remove trade barriers, modernize industry, improve European prosperity, and prevent the spread of Communism. The Marshall Plan required a lessening of interstate barriers, a dropping of many regulations, and encouraged an increase in productivity, trade union membership, as well as the adoption of modern business procedures. [SEP] Knowledge 2: Black Death
The Black Death is thought to have originated in the arid plains of Central Asia, where it then travelled along the Silk Road, reaching Crimea by 1343. From there, it was most likely carried by Oriental rat fleas living on the black rats that were regular passengers on merchant ships. Spreading throughout the Mediterranean and Europe, the Black Death is estimated to have killed 30 -- 60% of Europe's total population. In total, the plague may have reduced the world population from an estimated 450 million down to 350 -- 375 million in the 14th century. The world population as a whole did not recover to pre-plague levels until the 17th century. The plague recurred occasionally in Europe until the 19th century.
Knowledge 1: Marshall Plan
The Marshall Plan (officially the European Recovery Program, ERP) was an American initiative to aid Western Europe, in which the United States gave over $12 billion (nearly $100 billion in 2016 US dollars) in economic assistance to help rebuild Western European economies after the end of World War II. The plan was in operation for four years beginning on April 3, 1948. The goals of the United States were to rebuild war - torn regions, remove trade barriers, modernize industry, improve European prosperity, and prevent the spread of Communism. The Marshall Plan required a lessening of interstate barriers, a dropping of many regulations, and encouraged an increase in productivity, trade union membership, as well as the adoption of modern business procedures. [SEP] Knowledge 2: Black Death
The most widely accepted estimate for the Middle East, including Iraq, Iran and Syria, during this time, is for a death rate of about a third. The Black Death killed about 40% of Egypt's population. Half of Paris's population of 100,000 people died. In Italy, the population of Florence was reduced from 110–120 thousand inhabitants in 1338 down to 50 thousand in 1351. At least 60% of the population of Hamburg and Bremen perished, and a similar percentage of Londoners may have died from the disease as well. Interestingly while contemporary reports account of mass burial pits being created in response to the large numbers of dead, recent scientific investigations of a burial pit in Central London found well-preserved individuals to be buried in isolated, evenly spaced graves, suggesting at least some pre-planning and Christian burials at this time. Before 1350, there were about 170,000 settlements in Germany, and this was reduced by nearly 40,000 by 1450. In 1348, the plague spread so rapidly that before any physicians or government authorities had time to reflect upon its origins, about a third of the European population had already perished. In crowded cities, it was not uncommon for as much as 50% of the population to die. The disease bypassed some areas, and the most isolated areas were less vulnerable to contagion. Monks and priests were especially hard hit since they cared for victims of the Black Death.

Answer: 30% to 65%