(a) Rent ceilings are abolished, except that the housing provider may implement, in accordance with § 42-3502.08(g) , rent ceiling adjustments pursuant to petitions and voluntary agreements approved by the Rent Administrator prior to August 5, 2006. Petitions and voluntary agreements pending as of August 5, 2006, shall be decided pursuant to the provisions of this subchapter in effect prior to August 5, 2006, and may be implemented in accordance with § 42-3502.08(g) . In considering a hardship petition pursuant to § 42-3502.12 , any unimplemented rent charged increase pursuant to a petition or voluntary agreement approved by the Rent Administrator shall be included in the maximum possible rental income. Except to the extent provided in subsections (b) and (c) of this section, no housing provider of any rental unit subject to this chapter may charge or collect rent for the rental unit in excess of the amount computed by adding to the base rent not more than all rent increases authorized after April 30, 1985, for the rental unit by this chapter, by prior rent control laws and any administrative decision under those laws, and by a court of competent jurisdiction. No tenant may sublet a rental unit at a rent greater than that tenant pays the housing provider.