Shares of Speedway Motorsports Inc. shot up 33% toward an 13-month high in morning trade Wednesday, enough to pace the NYSE's gainers, after the racetrack owner and operator said it received a buyout bid from Sonic Financial Corp. that values the company at about $734.6 billion. Sonic is Speedway's largest shareholder, with 58% of the shares outstanding, according to FactSet. Sonic is offering to pay $18 for each Speedway share outstanding that it doesn't already own, a 29% premium to Tuesday's closing price of $13.94. Speedway said it has formed a special committee of independent directors to consider the buyout proposal. The stock has now gained 1.8% over the past 12 months, while the Dow Jones Industrial Average has climbed 11%.