By Karlee Weinmann (July 18, 2013, 3:17 PM EDT) -- The billionaire behind activist investor Trian Fund Management LP said at a New York conference that he is pushing PepsiCo Inc. to pay up to $67.8 billion to acquire Mondelez International Inc., the snack company behind Oreo cookies and other products, Bloomberg reported on Thursday. Speculation has swirled over what Nelson Peltz has in store for PepsiCo after he bought a sizable stake in the company — and in Mondelez — earlier this year. A previously agreed-upon period for closed-door talks with the soft drink giant closed this week, stoking rumors that Peltz would flex his muscle to force a tie-up. Peltz's combined stakes are worth more than $2 billion....