Final answer:
Upon completion of the building, if you agreed to the additional $25,000 demand from Sam, then you would owe a total of $125,000. This new total is a result of the amended agreement between you and Sam.
Step-by-step explanation:
The scenario presented involves a contractual agreement between you and Sam for the construction of a building. Initially, you both agree on a price of $100,000 for the complete construction. At 75% completion, Sam demands an additional $25,000 to finish the building. Assuming you agreed to Sam's demand, legally, this can be seen as an amendment to the original contract or as a new supplementary agreement. Therefore, upon completion of the building, you would owe Sam $125,000, which includes the original agreed price plus the additional amount requested.
It is important to note that such an agreement should be documented in writing to avoid any future misunderstandings or disputes regarding the terms of the agreement. If you had verbally agreed to pay the additional $25,000, it may be enforceable if evidences like emails, messages, or witnesses exist, though written contracts are always preferable in business transactions.
Considering similar scenarios such as those outlined where house values change over time or portions of loans are paid off, it's clear that the final amount owed or owned in any financial transaction can be affected by agreements and changes that occur after the initial deal is made. Situations in real estate like Freda's increased house value and Frank's equity in his home are examples of similar considerations of value after changes in circumstances.