D) $1,360 E $790 21. An isocost line shows all of the labor-capital combinations that A) are below the firm's marginal rate of technical substitution. B) have the same total cost. C) deliver technically efficient production. D) produce the same output amount. E) isolate the firm's external costs. Page 11 21. An isocost line shows all of the labor-capital combinations that A) are below the firm's marginal rate of technical substitution. B) have the same total cost. C) deliver technically efficient production. D) produce the same output amount. E) isolate the firm's external costs