After setting up conversion tracking, you want to add a column for conversion value per cost. How would that be calculated?

It would be calculated by dividing the total conversion value by the total cost of all ad interactions.
It would be calculated by dividing the total conversion value by the number in the conversions column.
It would be calculated by dividing the total cost by the number in the conversions column.
It would be calculated by dividing the number in the conversions column by the total eligible interactions.