Academic C project

This is an simple academic project and requires few lines of C code to be added to the FIR filter code. The project is due in another week for me. Could you be able to help me out? The project is about CD to DAT Sample rate conversion, the professor has given us the FIR code to be edited with the hints in fir.c file. Please see the attached pdf file for more information and the attached .tar file is the project.