4. (10 points) Consider a onetime change in government policy that immediately and permanently increases the level of the labor force in an economy (e.g., a more generous immigration policy) from L0 to L1 at some point in time to. Assuming the economy with technological progress at a rate g starts in its initial steady state, use the Solow model to explain what happens to the economy over time and in the long run. In particular, draw two diagrams: 1) for real interest rate with time on the horizontal axis using a ratio scale and 2) the Solow diagram that outlines the changes. Assume that the growth rate of population stays constant over time at a rate n (as would be the case, e.g., if immigrants and native population have the same birth and death rates)