Activities: [(1,4), (3,5), (0,6), (5,7), (8,9), (5,9)]. Sorted by end time: [(1,4), (3,5), (0,6), (5,7), (5,9), (8,9)]. Select (1,4). Last end = .
(3,5): start < . Conflicts. Skip.
(0,6): start < . Conflicts. Skip.
(5,7): start >= . Select! Last end = .
(5,9): start < . Conflicts. Skip.
(8,9): start >= . Select! Last end = . Selected: (1,4), (5,7), (8,9). Count: . Notice each selection extends the timeline minimally.