Design Frequency modulation and demodulation for two signal a speech and single tune sinusoidal signals using MATLAB

the modulation part I did it with our method that I learned (check it out also) , but the main issue facing me with the demodulation part give incorrect outputs (not return the signal back) maybe the DC blocker or the LPF having wrong selected values . Answer the all the parts and give explanation of what is done. JUST understanf the code and FIX IT so I get good recovery of signals .

Follow the instruction carefully .

I provided my code and explain above what the problem in it .

provide the solution as MATLAB file or in PDF/docx so I can copy and paste it .