1. Create an ellipse as shown in figure on top plane.
2. Extrude the feature with given dimensions.
3. Now on front plane extrude the following sketch.
4. In the extrude feature dialogue box, make sure that the 'Merge Result' check box is unchecked.
5. Now use the "Combine" command ('Insert> Features> Combine') to select the common out of the two entities.
6. Now on the top plane, sketch an ellipse to create the finger cavity in the ring. Use offset entities command in the sketcher for quicker approach.
7. Cut Extrude the sketch in both directions.
8. Create a datum plane offset at 10mm from the right plane and sketch the following on it.
9. Reverse the direction of cut extrude feature as desired and extend the feature upto the inner surface of the ring.
10. Add the necessary fillets and the model is done.