Activist investor Arkhouse Management Co. is urging Barry Diller's media company, IAC Inc., to conduct a share buyback and sell its New York City office building to boost its stock price. In a letter sent Wednesday to IAC Chairman Barry Diller, Arkhouse stated that the value of the company's assets "far exceeds" its current share price and urged the board to repurchase at least $750 million in shares through a Dutch auction tender offer.