OPINION OF THE COURT

Maicol Avarez challenges his sentence for conspiracy to distribute cocaine and crack cocaine. He argues that the downward departure for his cooperation is not sufficiently significant, that the District Court failed to consider all relevant factors in making the departure, that the District Court failed to consider one of his departure requests, that the District Court made an arithmetical error in calculating *755 his sentence, and that he is entitled to resentencing under United States v. Booker, 543 U.S. - , 125 S.Ct. 738, 160 L.Ed.2d 621 (2005).

Having determined that issues with respect to Booker are best determined by the District Court in the first instance, we vacate the sentence and remand for resentencing in accordance with that opinion. Because we vacate the sentence, we do not reach Alvarez’s non -Booker sentencing challenges. We note, however, that any challenge to the conviction has been waived, and we therefore affirm the conviction.