Final answer:
The AD-AS Model, or Aggregate Demand-Aggregate Supply model, is generally attributed to John Hicks, who adapted the ideas from Keynesian economics. The economic philosophies of John Maynard Keynes, Adam Smith, Milton Friedman, and Friedrich Hayek have all contributed to shaping the U.S. free enterprise system.
Step-by-step explanation:
The AD-AS Model, which stands for Aggregate Demand-Aggregate Supply model, was not the creation of a single economist but is a framework that has been developed over time. While John Maynard Keynes is one of the most influential economists in modern times, he did not directly develop the AD-AS model. Keynes contributed greatly to macroeconomic theory, particularly with his work during the 1930s that led to Keyensian economics, which was originally explained using the expenditure-output approach. The AD-AS model, incorporating ideas from Keynesian economics, was further developed later on. So, of the listed economists, John Hicks is often credited with the development of the AD-AS model, particularly his IS-LM model which is related to Keynes's work.
The economic philosophies of the mentioned figures have contributed to the current U.S. free enterprise system. John Maynard Keynes proposed government intervention to manage economic cycles, while Adam Smith championed laissez-faire economics. Milton Friedman and Friedrich Hayek advocated for limited government intervention and free market principles. These differing philosophies have shaped the debate on the role of government in the economy and have influenced the development of economic policy in the United States.