Where a district court applies a federal sentencing enhancement based on findings of fact at sentencing—and neglects to explain how it selected among competing plausible inferences—does a generic abuse-of-discretion standard of review adequately protect the defendant's Sixth Amendment right to a jury?

Whether a district court's fact-finding at sentencing that lacks explicit reasoning for selecting among competing inferences violates a defendant's Sixth Amendment right to a jury trial when applying sentencing enhancements