On October 7, 1980, John and Joan Johnson (plaintiffs) traded in their truck for a new Chevrolet truck manufactured by General Motors Corporation (GMC) (defendant). After the trade-in value was deducted, the Johnsons paid $4,202.10 for the new truck. On the way home from the dealership, the Johnsons began experiencing trouble with the new truck. They had the problems fixed, but the troubles continued. On November 30, 1980, the Johnsons revoked their acceptance of the deal and tried to return the truck for a full refund. GMC declined. The Johnsons filed suit, seeking to revoke their acceptance of the purchase. The Johnsons continued to use the truck while the suit was pending. In all, the Johnsons drove the truck 14,619 miles after revoking their acceptance of the sale. At trial, GMC introduced a Federal Highway Administration (FHA) guide regarding the costs of owning a car or truck. The guide stated that a truck similar to the Johnsons’ would cost approximately 33.2 cents per mile to own. The trial court ruled that the Johnsons could revoke their acceptance, but that GMC was entitled to a setoff of $4,702.94 due to the Johnsons’ continued use of the truck after their revocation. The trial court did not award the Johnsons prejudgment interest. The Johnsons appealed.