VW truck unit Traton offers $2.9 billion to take over Navistar

(Reuters) - Volkswagen AG's Traton commercial truck unit said on Thursday it had offered $35 a share, or $2.9 billion (2.21 billion pounds), for the shares of U.S. truck maker Navistar International that it does not already own, and investors bet the bid will go higher.Navistar shares shot up by 50% to just over $36 a share in after-hours trading following Traton's proposal, suggesting investors expect a potential deal could be richer than Traton's opening offer. Traton said its offer was..