Jefferies (JEF) shares soared 5.8% in the last trading session to close at $70.36. The move was backed by solid volume with far more shares changing hands than in a normal session. This compares to the stock's 12.1% gain over the past four weeks.Jefferies has agreed to Sumitomo Mitsui Financial Group’s proposal to increase its stake in the U.S. investment bank. Per a Bloomberg report, citing people familiar with the matter, the Japanese lender, which already owns roughly 15% of Jefferies, is considering inv ...