How well does von Thünens model apply to the U.S on a national scale? Explain

In the Romer Model (1990), if the level of technological knowledge is 1000, productivity parameter in the R&D sector is 0.0001, and wage paid to human capital is 50, what is the price of a new design from the R&D activities? (Show calculation steps.) In the Romer Model (1990), suppose the productivity parameter in the R&D sector is 0.0001 and the stock of human capital in the economy is 5000, of which 4000 is allocated to the manufacturing of the final goods. In the final goods production sector, output elasticity with respect to labor is 0.3 and output elasticity with respect to human capital is 0.5. Find the equilibrium interest rate. (Show calculation steps.)

Briefly discuss drawbacks of Solow model?

For each of the following scenarios, use the graphical depiction of the Malthusian model to illustrate what happens to a country’s population size and per-capita income in the short run and in the long run. a. Scientists discover a new strain of wheat that can produce twice as much grain per acre. 
 b. A war kills half of the population. 
 c. A volcanic eruption kills half the people and 
destroys half the land.