a. Explain the concept of diminishing returns to physical capital. What does it predict about economic growth of different countries over time? Give two real world examples of countries that are in line with this prediction, and one that contradicts this prediction.

b. How is the concept of diminishing returns to physical capital similar to, and how is it different from, the concept of decreasing returns to scale? Which one of these features is more likely to be observed in real-world economies, and why?

There is no need to write whole lot of details, please just answer briefly and to the point.