Study question on AS-AD Model: Please Consider the short-run model of the economy

a. The key difference between the long-run and short-run model is the assumption that prices are flexible. In the short-run prices are assumed to be fixed or, at least, prices are expected not to fall. Why might prices be sticky downward?

b. The short-run aggregate supply curve is thought to be upward sloping, at least above the full employment level of output. Compare that to the long-aggregate supply curve and explain why the two might differ.

c. In the short-run model it is generally assumed that price levels do not change. How then does the economy move to an equilibrium level of GDP? please explain this in words

d. Suppose consumer wealth falls because the stock market takes a nosedive. If the economy begins at full employment, how does that affect GDP? Please help describe the process and the outcome.