Here's what I did.
Import the bit map.
1. Draw an arc and node edit until it matches the lower edge of the lower line. Draw a vertical center line through the arc.
2. Offset the arc upward to make the upper edge of the lower line.
3.Draw lines to trace the prongs on the left. Mirror to the right about the vertical center line .
4. Draw lines to outline the center prong. Note that as drawn, it is not centered on the arc. Use the Align Selected Objects tool to center the prong horizontally on the arc.
5. Use the Vector trim and the Extend Vectors to a common point tools to finish off the outline.
6. Join Vectors to make a single vector outline.
Good judgement comes from experience.
Experience comes from bad judgement.