Provide a single, simplified entry point in front of a set of complex subsystems, so callers don't need to know the CPU, Memory and Disk have to be driven in a specific order.
Implement `ComputerFacade.start()`/`shutdown()`, each calling the three subsystems (CPU, Memory, Disk) in the right order and collecting their return values.
solve(action) builds a ComputerFacade and calls start() or shutdown().
Sample tests