 Shares of Rite Aid Corp. RAD, 13.78 rocketed as much as 38.5 intraday before paring gains to be up 18.7 in very active afternoon trading Wednesday, after the New York Post reported that the drugstore chain rejected earlier this month a buyout bid that valued the company at more than 800 million. Trading volume swelled to about 16 million share, compared with the full-day average of about 4.3 million shares. 