Order, Supreme Court, New York County (Whitman, J.), entered October 24, 1980, which denied plaintiff’s motion for summary judgment on his first cause of action, reversed, on the law, and motion granted, with costs. Defendant bank held a first mortgage which was in default on a commercial building. The deceased, a licensed real estate broker, introduced McDonald’s Corporation to the bank as a prospective purchaser of the mortgage or the fee. A letter agreement was executed which provides in pertinent part, “My commission for the sale of the property or for the assignment of your mortgage to McDonald Corporation [or its nominee] shall be $10,000.00 to be due at the time of title closing if the deal entails the sale of the property or at the time of assignment of your mortgage if the deal entails the sale of same.” A nominee of McDonald’s Corporation purchased the property at the foreclosure sale, at a price which covered the debt owed to the bank and all of its expenses in connection with the sale. This action was commenced to recover the brokerage commission. The bank asserted that the agreement was ambiguous and that the discussions between decedent and the bank centered on the bank’s selling of property to McDonald’s directly, in the event the bank was the successful bidder at the foreclosure sale, and did not contemplate McDonald’s nominee purchasing at the foreclosure sale. The bank never bid at the sale. It is our view, in the context of the situation prevailing at the time of the agreement, that just such a purchase as occurred is one of the alternatives which reasonably must have been contemplated by the agreement. The bank is attempting to contradict said agreement by the use of parol evidence. It submitted an affidavit by one of its vice-presidents who “dealt personally with plaintiff’s decedent” (not the vice-president, however, who signed the letter agreement), which provided no details as to any meetings or conversations between the parties. Its contention that the parties “had in mind” a particular condition is little more than a conclusion. The defendant bank did not disclose in evidentiary form the particular parol evidence, if any, on which it relied (Mallad Constr. Corp. v County Fed. Sav. & Loan Assoc., 32 NY2d 285, 290; see, also, Ehrlich v American Moninger Greenhouse Mfg. Corp., 26 NY2d 255, 259). A motion for summary judgment based upon a contractual obligation may not be defeated solely by the allegation that the contract is ambiguous. The party opposing summary judgment must set forth extrinsic evidence upon which it will rely to support the construction it urges, otherwise there are only documents to interpret. “[W]here a question of intention is determinable by written agreements, the question is one of law, appropriately decided by an appellate court * * * or on a motion for summary judgment. Only where the intent must be determined by disputed evidence or inferences outside the written words of the instrument is a question of fact presented”. (Mallad Constr. Corp. v County Fed. Sav. & Loan Assoc., supra, at p 291.) Concur — Kupferman, J.P., Sullivan and Carro, JJ.