Prior to filing a voluntary Chapter 7 bankruptcy petition, Haynes Company pays a supplier $13,000 to satisfy an unsecured claim. Haynes was insolvent at the time. Subsequently, the trustee appointed to oversee this liquidation forces the return of the $13,000 by the supplier. Which of the following is true?

  a. A preference transfer has been voided.
  b. All transactions just prior to a voluntary bankruptcy proceeding must be nullified.
  c. The supplier should sue for the return of this money.
  d. The $13,000 claim becomes a liability with priority.