Johnson's rule: short A-times first, short B-times last

There are 6 jobs each of which must go through the two machines A and B in the order AB. The processing times (in hrs) are: job 1: $(4,6)$; job 2: $(8,3)$; job 3: $(3,7)$; job 4: $(6,2)$; job 5: $(7,8)$; job 6: $(5,4)$ (times on A, B). Write down the sequence of jobs that minimizes the total elapsed time required to complete the job.