A machine shop has two machines, A and B. Four jobs need to be processed through machine A first and B second. Job 1 will take one hour on machine A and three hours on machine B. Job 2 will take three hours on A and two hours on B. Job 3 will take seven on A and three on B. Job 4 will take five hours on A and one hour on B. Using Johnson’s rule, in what order should these jobs be done?