Shares of Biogen Inc BIIB.O surged 42.741.7% on news that the Food and Drug Administration approved its Alzheimer's disease drug aducanumab. By Stephen Culp NEW YORK, June 7 (Reuters) - Wall Street started the week mixed on Monday as buyers stood on the sidelines on news of a global minimum corporate tax rate and lingering inflation fears, and a lack of market-moving catalysts. Lawmakers in Washington are doubling down on efforts to craft a bipartisan infrastructure spending package, with House Democrats expected to bring a bill to vote as early as Wednesday.