Warren Buffett's Berkshire Hathaway Inc. is reaching into its deep pockets to give a steadying hand to Constellation Energy Group Inc. and, at the same time, grab a bargain. Berkshire's MidAmerican Energy Holdings Co. said Thursday it will buy Baltimore-based Constellation for $4.7 billion and give it an immediate $1 billion infusion after shares of the nation's largest wholesale power seller plummeted and liquidity concerns had analysts worried it would go out of business. "Obviously we're in unprecedented times," MidAmerican President and CEO Gregory Abel said. "Liquidity and solvency issues are a top priority for many companies. We don't have...