Marginal rate of technical substitution a. is always equal to the slope of the iso-cost line at a particular combination of inputs. b. is the number of units of one input it takes to produce another unit of output. c. is always equal to the negative of the ratio of the wage to the rental rate of capital at the cost-minimizing combination of inputs. d. is always greater than or equal to zero. The net reduction in total welfare from a loss of surplus by one group that is not offset by a gain to another group is called a. Deadweight loss b. Welfare loss c. Market failure d. Politics as usual lfthe demand curve is horizontal, demand is said to be a. perfectly inelastic. b. perfectly elastic. c. perfectly competitive. d. perfectly understandable