The four balls, each of mass m = 2.8 kg, are rigidly mounted to the rotating frame and shaft, which are initially rotating freely about the vertical z-axis. What is the total angular momentum of the system?
a) 0 kg m²/s
b) 11.2 kg m²/s
c) 5.6 kg m²/s
d) 22.4 kg m²/s