What is the formula of the mean diameter at the position of centre of gravity?

• A. mean diameter at the position of centre of gravity = Inner diameter + diameter of stator wires
• B. mean diameter at the position of centre of gravity = Inner diameter * diameter of stator wires
• C. mean diameter at the position of centre of gravity = Inner diameter / diameter of stator wires
• D. mean diameter at the position of centre of gravity = Inner diameter ‚Äö√Ñ√∂‚àö√ë‚àö¬® diameter of stator wires