The overall reliability of the checkout system is calculated to be 0.98 multiplied by 0.92 times 0.90, or 0.8332. The store manager can ensure that the system is reliable at least 90 percent of the time by dedicating two of the store's final check-out registers to the process. There are trade-offs involved in increasing the reliability of a system. More reliable components usually cost more. Redundant systems are usually more complex and more expensive. For example, a system with a reliability of 0.8332 is said to be 83.32 percent reliable.