Final answer:
Without specific reliability data for both design A and B, it is impossible to determine which design has a higher reliability; however, generally speaking, design B with backup units should theoretically have a higher reliability.
Step-by-step explanation:
When deciding between product design A and design B, which has backup units for its components, the reliability of each design must be compared. Reliability in engineering refers to the probability that a product will perform its intended function under specified conditions for a designated period of time. Backup units are a redundancy strategy aimed at improving product reliability by providing a substitute in the event of a main component failure.
Generally, a design with built-in redundancies, such as backup units, would typically have a higher reliability than a design without such features because these backups can take over if a primary component fails. However, without explicit reliability figures or probabilities for failures of the individual components for both design A and design B, we cannot conclusively determine which design has the higher reliability. The context provided insufficient information on design A to make a fair comparison.