Explain the intuition behind why the aggregate demand curve is downwar

Explain the intuition behind why the aggregate demand curve is downward sloping. Why does an increase in the money supply shift the aggregate demand curve to the right?

What will be an ideal response?

ANSWER

According to the quantity theory, holding the velocity and supply for money constant, a lower price level means that the same level of money can conduct more transactions, so the level of transactions increases. An increase in the money supply means that a higher level of transactions can be supported for every value of the price level.