How to shorten the code for function with varying single parameter input to plot them on the same screen

Hello,

There is a y (pressure) function with one output that changes depending on input variable x (pipe diameter). I have three different input variable x. I need to plot the the variation of y function across the parameter z using the three different parameters x on the same plot. These parameters will be displayed as legend. I wrote 3 three different codes for y functions for different x values . But it is too lengthy. Is there short way to do it? You can see the results in the file attached.

[Rik]

How is your code too lengthy? And what is your code? It seems like it gets the job done. Is it too slow? Is it too difficult to understand for a third party reading your code?