TOEFL® writing: The difference between Macroeconomics and Micoroeconomics

[Ilovepsycho]

I wrote this, and I would like you to revise my writing gramatically.
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I bought a book Macroeconomics 6/E written by N. Gregory Mankiw, professor of economics at Havard University, known for the book Principles of Economics which was translated in Korean 맨큐의 경제학.

Today I have studied some parts of 'Chapter 1: The science of Macroeconomics', and there was three questions for review on the last page of this chapter: 1. Explain the difference between macroeconomics and microeconomics. 2. Why do economists build models? 3. What is a market-clearing model? When is it appropriate to assume that markets clear?

From now, I will answer the first question. Macroeconomics is the study of the economy as a whole. It addresses growth in incomes such as Real GDP, changes in prices such as the inflation rate, and the unemployment itself or its rate.
Microeconomics, however, focuses on individuals' and firms' decisions in optimizing the former's utility or the latter's profit on the underlying assumption that everyone is absolutely rational, and on their interactions in the marketplace.

The End.