Last year, 1,000 cases of cough syrup were sold at $10; this year, 1,2000 cases were sold at $12 . the most probable interpretation of these data is that the:

a. supply curve has shifted to the left, with no change in demand

b. demand curve has shifted to the right, with no change in supply

c. supply and demand curves are shifting to the left

d. supply and demand curves are shifting to the right

Need help for my homework. Thanks