Please help me build parts of my code. Requires a bit of time

I need a couple of things that I need to make some stuff:

At y=100, I need four flat lines of different lengths.

The first line should go from (0,0) to (40,0)

The second line should go from (50,0) to (70,0)

The third line should go from (70,0) to (80,0)

The fourth line should go from (85,0) to (90,0)

The second thing is when you see purple points generated, I want the code to cancel if the line hits those points.

The third thing is I want the line to go left from points (0.0) to (50,0) and right from points (51,0) to (100,0)

Please let me know how I should go about doing this stuff. The code needed for review is attached.

[Walter Roberson]

plot([0 40 nan 50 70 80 nan 85 90], [0 0 nan 0 0 0 nan 0 0], '*-')