Explain what happens to the demand curve for air transportation between New York City and Washington, D.C., as a result of the following events: Thoroughly explain your answer and provide at least 2 situational examples and analysis for each one.

The income of households in Metropolitan New York and Washington, D.C., increases 20%; the U.S. Government subsidizes Amtrack, and the cost of train ticket between New York City and Washington, D.C., is reduced 50%; the number of business with both New York City and Washington, D.C., doubles; the price of an airline ticket decreases 20%.