Five jobs are waiting to be run. Their expected run × are 9, 6, 3, 5. In what order should they be run to minimize average response time? (Your answer will depend on x.)
a) 3, 5, 6, 9
b) 5, 3, 6, 9
c) 6, 5, 3, 9
d) 6, 3, 5, 9