Segment AB:

Segment BC:

Segment CD:

To draw the shear diagram:

1. At segment AB, the shear is uniformly distributed at 1900 lb.
2. A shear of -100 lb is uniformly distributed over segments BC and CD.

To draw the Moment Diagram:

1. M_AB = 1900x is linear; at x = 0, M_AB = 0; at x = 3 ft, M_AB = 5700 lb·ft.
2. For segment BC, M_BC = -100x + 6000 is linear; at x = 3 ft, M_BC = 5700 lb·ft; at x = 9 ft, M_BC = 5100 lb·ft.
3. M_CD = -100x + 1200 is again linear; at x = 9 ft, M_CD = 300 lb·ft; at x = 12 ft, M_CD = 0.