The binding legal principles established are: (1) A term expressly included in a sale agreement describing the goods to be sold is a term of that agreement, and obligations to fulfill that term undertaken by the seller's agent for delivery are obligations under the sale agreement, not separate severable agreements. (2) Where a term in a sale agreement was important to the contracting parties, even if it might objectively seem minor, breach of that term goes to the root of the contract and entitles the innocent party to cancel the contract and claim restitution, not merely damages. (3) In restitution claims following cancellation of a sale agreement, mora interest on payments made pursuant to legal obligation under the agreement runs from the date of cancellation to the date of repayment. (4) Mora interest on payments made after cancellation of an agreement, where there is no legal obligation to make such payments, runs only from the date of judgment ordering restitution to the date of repayment. (5) Once an agreement is cancelled and restitution is sought, the risk of deterioration of goods to be returned passes to the party receiving them back, subject to the returning party not having used the goods after cancellation.