What is the mandatory minimum sentence for possession with intent to distribute methamphetamine under section 841(b)(1)(B)(viii) of the Federal Drug Code?

On November 20, 1989 defendant entered a plea of guilty to possession with intent to distribute approximately 29 grams of methamphetamine contained in a liquid solution of 192 grams. The district court sentenced defendant under 21 U.S.C. Sec. 841(b)(1)(B)(viii) to the mandatory minimum term of five years imprisonment and four years supervised release. The district court's interpretation of section 841(b)(1)(B)(viii) is reviewed de novo. United States v. Valencia-Roldan, 893 F.2d 1080 (9th Cir.1990), cert. denied, --- U.S. ----, 110 S.Ct. 2181, 109 L.Ed.2d 509 (1990).