MPK x k. Therefore, the wage per efficiency unit in the two countries is equal. Workers, however, care about the wage per unit of labor, not the wage per efficiency unit. Another growth model question. This is easy to find in your text.
Fluctuations are due to shocks to the aggregate supply curve.
See your notes and the text for details. Staggered price adjustments significantly slows the adjustment of the price level after a monetary contraction. The result of these incremental changes is that even after every firm in the economy has gone through one round of price adjustment, the aggregate price level will not have fully adjusted to its new equilibrium level. Real business theory assumes that the price level is fully flexible. Only the price level is free to adjust to ensure that the money market clears.