May a Section 1 claim be dismissed pursuant to Fed. R. Civ. P. 12(b)(6), consistent with Twombly, based on evidence suggesting an alternative, non-conspiratorial reason for the challenged conduct, where the complaint also contains substantial factual allegations disputing that alternative inference?

To adequately allege anticompetitive conduct for purposes of a Section 2 claim involving a threatened refusal to deal, must plaintiffs allege a "substantial foreclosure" of competition?

May a Section 1 claim be dismissed pursuant to Fed. R. Civ. P. 12(b)(6), consistent with Twombly, based on evidence suggesting an alternative, non-conspiratorial reason for the challenged conduct, where the complaint also contains substantial factual allegations disputing that alternative inference?