Answer:
By formation of legally binding contract.
Explanation:
Contacts are a good way for procuring inputs that have well-defined and measurable quality specifications and require highly specialized investments. Because of the high quality expected in the goods procured, having a legally enforceable contact will make the vendor provide high quality products that meets required specifications.
However when contracts dictate a particular price, so if the market price of input were to go down we will still be obligated to buy at the higher price from the vendor.
