how to make multiple line graphs in one chart based on column values

[libreoffice calc, version, linux]
I have a table with 3 numeric columns: memory, width, and time, 30 rows. I want, on one chart, a points-and-lines plot for each value of memory(about 5 distinct values). Vertical axis is time, horizontal axis is width.

I’ve not used this kind of plotting interface before, so my question is probably naive, but I can’t understand how to do this from the wizard F1 help.