$1-$ Eccentric speed reducer

The figure below shows a schematic representation of an eccentric speed reducer along with a kinematic model. The input member is D $($carrier$)$ which carries $2$ planets B and C$.$ Planet $B$ is in mesh with the fixed ring$-$gear $E$ whereas planet $C$ is in mesh with ring$-$gear $F$ connected to the output shaft G$.$

Figure $1-$ schematic of the eccentric speed reducer

The partial kinematic model in Figure $2$ is used. The actual meshing conditions between the planets and the ring$-$gears are replaced by no slipping conditions at I and $J.$

Introduce all the coordinate systems$/$parameters required and, supposing that the dimensions in Figure $2$ are to scale, give the speed ratio of the speed reducer.