Suppose the economy is in long-run equilibrium and there is an increase in investment. As a result, real GDP will in the short run, and in the long run. increase; decrease to its initial value decrease; decrease further increase; increase further decrease; increase to its initial level

The correct answers are: increase and decrease to its initial value.

As a result, real GDP will increase in the short run, and decrease to its initial value in the long run.

Explanation:

To begin with, the GDP is a monetary measure of the market value of all the final goods that a economy produces in a certain amount of time. Moreover, that measure is influeced by many variables and one of them turns out to be the investment that the country in general does. Therefore that when the investment in the country increases or decreases the GDP will be affected and that is why that when the there is an increase in the investment the real GDP will suffer and increase as well too in the short run and it will eventually decrease to its initial values in the long run.  

answer; closing the loop;

answer(b) equal; set period;