Hello, please add step by step with explanation correct answer. Will def rate thank you so much! A three stage planetary geartrain is shown below.

a$.$ Write out all rolling contact equation$($s$).$

b$.$ List the scalar variables.

c$.$ Deduce the number of degrees$-$of$-$freedom of the system. Note that body $2$ is held fixed.

d$.$ What is the gear ratio?

$($Hint: You only need to figure out the math for one stage, then extend the pattern.$)$