Mitchell’s substantial rights. As required by 21 U.S.C. § 851(b), the government filed an information prior to trial notifying the defendant that the government intended to increase his statutory penalty under 21 U.S.C. § 841(b) by using a 1993 conviction for attempted possession with intent to distribute cocaine. Section 851(c)(1) provides that if the defendant intends to contest the government’s use of a prior conviction to enhance the sentence, the defendant must file a written response to the government’s information and the court is required to have a hearing to resolve the dispute. Mitchell, however, filed no written response and did not contest the existence or validity of the prior convictions pursuant to § 851(c). See United States v. Williams, 298 F.3d 688, 693 (7th Cir.2002) (<HOLDING>). We also note that the presentence report
holding that failure to comply with  851b was harmless in part because defendant did not object to prior convictions listed in presentence report holding failure to comply with  851b was harmless error in part because defendant did not comply with  851c procedures for challenging prior convictions holding that plan did not comply holding the failure to comply with the act does not bar defendant from raising a constitutional challenge to jury selection procedures holding that failure to comply with  851b was harmless because defendant was properly put on notice that the government was seeking an enhancement and defendant concluded that no valid grounds existed for challenging the convictions or enhancement after research