According to the efficient-market theory, what effect would the following events have on the price of GM's stock?
a. A surprise announcement that the government is going to lower business taxes next July 1
b. A decrease in business taxes on July 1, 6 months after Congress passed the legislation
c. An announcement, unexpected by experts, that the United States will impose quotas on imports of Chinese cars during the coming year
d. Implementation of c by issuing regulations on December 31