Seventeen years ago, Susan designed a corrugated steel culvert for a rural road. Her work was accepted and paid for by the county engineering department. Last winter, the culvert collapsed as a loaded logging truck passed over. Although there were no injuries, there was damage to the truck and roadway, and the county tried unsuccessfully to collect on Susan’s company’s bond. The judge denied the claim on the basis that the work was done too long ago. This defense is known as