Which among the following is a violation of weak form efficiency?
a. Galleon Investments a hedge fund made millions of dollars each year by exploiting information from CEOs and top executives of companies they invested in.
b. Berkshire Hathaway, made a fortune based on annual reports published by companies.
c. Systematic Investors, a high frequency investment club made millions by trading based on price and volume information on companies.
d. Bernie Madoff made millions by firms which were likely to be bought by other companies.