to what extent are the fundamental principles of microeconomics (like law of demand, law of substitution, consumer surplus etc.) are applicable to macroeconomcs?

Question

please anyone provide me the answer as soon as possible.

Answer 1

They are nearly all applicable.
You and I will likely work more with higher wage rates (micro). A country's quantity of labor supplied will increase with higher wage rates (macro).
I receive some consumer surplus when I buy jelly beans (micro). The consumers of a country collectively get some surplus with all the aggregrate goods and services they consume (macro).
You and I have opportunity costs (micro), a country, collectively, has opportinity costs (macro).

And on and on.