Answer to Question 1
As the level of capital per hour worked increases, an economy moves along the per-worker production function toward higher levels of real GDP per hour worked. However, diminishing returns imply that successive increases in capital per hour work increase real GDP per hour worked at a decreasing rate. As shown in the graph below, moving from point A to point B implies an increase in capital per hour worked. As a result, real GDP per hour worked increases from 780 to 800 (an increase of 20 ). Moving from point B to point C implies a similar increase in capital per hour worked, but real GDP per hour worked increases from 800 to 810 (an increase of only 10 ). Without technological change that shifts the per-worker production function upward, continual growth in real GDP per hour worked cannot be sustained even if capital per hour worked continues to increase.
Answer to Question 2
D