Consider the figure 8.1, which is a family of average cost curves. The average total cost curve at a given level of output is shown by: Curve 4 Fig 8.1 Curve 1 Short-run average costs (dollars) Curve2 Curve3 Quantity O none of the below. the vertical distance between curve 1 and curve 2. the vertical sum of Curve 1 and Curve 3 at a given level of output. Othe vertical sum of Curve 2 and Curve 3 at a given level of output