concurring.
I agree with the majority that summary judgment for Valley Bank should be reversed. However, I would go further and direct that summary judgment be awarded in favor of Intermountain Brick Company.
*431The language in question is clear and unambiguous:
“This l[ie]n release includes all backc-harges, ([$]18,701.23), [pjayments made to Intermountain Brick through the Clerk of Court, Natrona County ([$]9,895.00) and Wyoming Block ([$]854.73)[.] Also your final retainage of $70,155.04[.]
“FINAL WAIVER OF LIEN
“I, the undersigned Etsel E. Sommer and Lyle Taggart, of Etsel E. Sommers & Valley Bank in consideration of the sum of $99,606.00, to be paid to me by WES-TATES CONSTRUCTION COMPANY, against the account of Etsel E. Sommers Masonry Construction and receipt of, will thereby be acknowledged, hereby waive and release all lien or right to lien now existing or that may hereafter arise from work or labor performed, or materials furnished on or before the 1st day of April 1986, for the improvement of the following described property situated in Natrona County, City of Casper, Wyoming — to wit: Natrona County Junior High School.” (Emphasis added.)
Valley Bank had a perfected security interest in Sommer’s accounts receivable. By signing the above final waiver of lien, Valley Bank specifically authorized Wes-tates Construction Company to pay Inter-mountain Brick Company the disputed $9,895. It waived and released its security interest in exchange for receiving the $70,-155.04 in retainage:
“Waiver can be determined as a matter of law where only one inference in regard to it may reasonably be drawn from the evidence introduced in the case, or from the undisputed facts. Moreover, where the only evidence as to waiver is a writing, its construction and interpretation and whether it constitutes a waiver is a question of law for the court.” 28 Am.Jur.2d, Estoppel and Waiver § 174 at 864-65 (1966).