This form shall be filed as required by §300.303 of this chapter with the trustee in a proceeding under section 5 of the Act by a broker-dealer who executed transactions out of which arose open contractual commitments, as defined by §300.300(c) of this chapter, with the debtor in the proceeding. The form shall be used to summarize the buy-ins and sell-outs of those open contractual commitments and shall be accompanied by the forms described in §§301.300b and 301.300c.