A thin rod of mass
M and length
a is free to rotate in horizontal plane about a fixed vertical axis
OO′. A thin circular disc of mass
M and of radius
a/4 is pivoted on this rod with its center at a distance
a/4 from the free end so that it can rotate freely about its vertical axis, as shown in the figure. Assume that both the rod and disc have uniform density and they remain horizontal during the motion. An outside stationary observer finds the rod rotating with an angular velocity
ω and the disc rotating about its vertical axis with angular velocity
4ω. The total angular momentum of the system about the axis
OO′ is
(Ma2ω48)n. The value of
n is