Within 20 days after service of a notice of opportunity for hearing which does not fix a date for hearing the respondent, either in the answer or in a separate document, may request a hearing. Failure of the respondent to request a hearing shall be deemed a waiver of the right to a hearing and to constitute consent to the making of a decision on the basis of such information as is available. [35 FR 10760, July 2, 1970, as amended at 51 FR 10386, Mar. 26, 1986]