Dist.Ct. erred in denying four defendants' motions for reduction in sentence under First Step Act, where Dist. Ct. found that said defendants were not eligible for said reduction in their sentences. Defendants were convicted of crack cocaine offenses, and each defendant was eligible for relief under First Step Act by having committed "covered offense," because: (1) each defendant had committed crack-cocaine offense prior to August 3, 2010; and (2) penalty for each crack-cocaine conviction had been modified by Fair Sentencing Act. Also, while Dist. Ct. indicated that it would not reduce sentence for one defendant, even if said defendant was eligible for relief under First Step Act, remand was still required for that defendant, because it was unclear whether Dist. Ct. had adequately considered said defendant's argument that reduction in sentence was justified because he had demonstrated exemplary pre-and-post-detention conduct, or because govt. had recommended sentence that was 10 percent below applicable guideline range.