Paul__B:
Sorry, you drew your graph wrong.You have put point B at 13 mA, not 15, and you have not drawn zero volts.
You are half right.
Point B according to instructions is the desired current which is 12.5mA.
But yes point C is wrong. I need 14 more divisions along the X axis since 1.5V == 0V.
So new graph
So then that gives me 5/.021 or 238.1Ω which must be what my current limiting resistor needs to be since that is very close to calculated value of
(V - Vf ) / I = R
( 5 - 2 ) / .0125 = R
R=240Ω
But I don't yet see the point of the load line.
Because if I just look at the original graph from the datasheet a current value of 12.5mA corresponds to a forward voltage of about 1.96V
So (5- 1.96) / .0125 = R
or 243.2Ω which is about as close as trying to draw a load line (at least as poorly as I draw).