If one of the three machines breaks down before starting the service, it would take the remaining two machines longer to meet the demand. If each machine can produce the same amount of material, it would take each machine 24 hours / 3 machines = 8 hours to perform the entire service.
So, with two machines working, it would take each machine 8 hours / 2 machines = 4 hours to complete the job. Thus, the total time to meet the demand would be 4 hours * 2 machines = 8 hours.