The following accompanying table shows the relationship between the speed of a computer's CPU and its benefits and costs. Assume that all other features of the computer are the same (that is, CPU speed is the only source of variation), and only the CPU speeds listed below are available for purchase. Total Marginal Total Marginal Benefit Benefit Cost Costs 3.5 $1,900 $1,500 $2,000 $400 The marginal benefit of upgrading from a 2.0GHz computer to a 2.56Hz computer is: Select one: Q a. $1,400. 0 b. $1,000. 0 c. $400. 0 d. $100