Defendant pleaded guilty to charge of conspiracy to distribute 500 grams or more of substance containing methamphetamine under sections 841(a)(1), 841(b)(1)(A), and 846. While defendant insisted that he had pleaded guilty to only conspiracy involving lesser quantity of drugs under section 841(b)(1)(B), record showed that defendant had admitted to facts implicating him in instant greater offense involving distribution of 500 grams or more of drugs in documents filed before plea hearing, at plea hearing itself, by admitting to facts in pre-sentence report and at sentencing hearing.