A manager has 20 different job orders, of which 7 must be assigned to production line I, 7 must be assigned to production line II and 6 must be assigned to production line III.
(a) In how many ways can the assignments be made?
(b) If the first job and the second job must be assigned to the same production line, in how many ways can the assignments be made?
(c) If the first job and the second job cannot be assigned to the same production line, in how many ways can the assignments be made?