Billionaire activist investor Carl Icahn has added Apple to the list of companies he hopes to turn into winners for his portfolio. That portfolio includes holdings in Dell, Nuance, Herbalife and Netflix, among others. On Tuesday [Aug. 13], Icahn tweeted, “Had a nice conversation with [Apple CEO] Tim Cook today. Discussed my opinion that a larger buyback should be done now. We plan to speak again shortly. We currently have a large position in Apple. We believe the company to be extremely undervalued.” Apple’s share price rose 5% following Icahn’s Twitter announcement.