What are the two basic variables of a demand schedule and curve?

The following set of questions refers to consumer demand for a product or service:

a. What are the two basic variables of a demand schedule and curve?

b. What is the law of demand?

c. Why does a demand curve slope downward?

d. According to the law of demand, what is the only thing that will cause a change in the quantity demanded of a good or a service?

e. What are the five determinants of demand listed in the text?