11 U.S.C. § 506 : US Code - Section 506: Determination of secured status

      (a)(1) An allowed claim of a creditor secured by a lien on
    property in which the estate has an interest, or that is subject to
    setoff under section 553 of this title, is a secured claim to the
    extent of the value of such creditor's interest in the estate's
    interest in such property, or to the extent of the amount subject
    to setoff, as the case may be, and is an unsecured claim to the
    extent that the value of such creditor's interest or the amount so
    subject to setoff is less than the amount of such allowed claim.
    Such value shall be determined in light of the purpose of the
    valuation and of the proposed disposition or use of such property,
    and in conjunction with any hearing on such disposition or use or
    on a plan affecting such creditor's interest.
      (2) If the debtor is an individual in a case under chapter 7 or
    13, such value with respect to personal property securing an
    allowed claim shall be determined based on the replacement value of
    such property as of the date of the filing of the petition without
    deduction for costs of sale or marketing. With respect to property
    acquired for personal, family, or household purposes, replacement
    value shall mean the price a retail merchant would charge for
    property of that kind considering the age and condition of the
    property at the time value is determined.
      (b) To the extent that an allowed secured claim is secured by
    property the value of which, after any recovery under subsection
    (c) of this section, is greater than the amount of such claim,
    there shall be allowed to the holder of such claim, interest on
    such claim, and any reasonable fees, costs, or charges provided for
    under the agreement or State statute under which such claim arose.
      (c) The trustee may recover from property securing an allowed
    secured claim the reasonable, necessary costs and expenses of
    preserving, or disposing of, such property to the extent of any
    benefit to the holder of such claim, including the payment of all
    ad valorem property taxes with respect to the property.
      (d) To the extent that a lien secures a claim against the debtor
    that is not an allowed secured claim, such lien is void, unless - 
        (1) such claim was disallowed only under section 502(b)(5) or
      502(e) of this title; or
        (2) such claim is not an allowed secured claim due only to the
      failure of any entity to file a proof of such claim under section
      501 of this title.