急急急~关于算法动态规划的问题~

[poliscat27]

这道题想了两天死活不会 麻烦帮看看谢谢啦
关于flow shop scheduling的

Let I be any instance of the two-processor flow shop problem.
(a)show that the length of every POFT（preemptive optimal finish time ） schedule for I is the same as the length of every OFT(optimal finish time) schedule for I.
(b)show that there exists an OFT schedule for I in which jobs are processed in the same order on both processors.