Sub directories in PROS

folder structure

│   │   auto.c
│   │   init.c
│   │   opcontrol.c
│   │   Makefile
|   └───foo
|        |    bah.c
│   │   API.h
│   │   main.h
|   └───foo
|        |    bah.h

How exactly would I modify the makefile to search subdirectories of src? right now the code works if I put foo.c in src however does not work in the state presented above. Therefore it isn’t a problem with the code.

I somehow missed this while researching my bad. I will leave this here to hopefully prevent others from missing it.
edit: words