For each of the following, identify where demand is elastic, inelastic, perfectly elastic, perfectly inelastic, or unit elastic:

a. Price rises by 10 percent, and the quantity demanded falls by 2 percent.

b. Price falls by 5 percent, and the quantity demanded rises by 4 percent.

c. Price falls by 6 percent, and the quantity demanded does not change.

d. Price rises by 2 percent, and the quantity demanded falls by 1 percent.