Figure 3-1 Graph (a) Graph (b) Two production possibilities frontier curves of Couches versus Chairs. A production possibilities frontier curve of Couches versus Chairs starts on the Couches axis at the maximum feasible value for couches, and descends in a concave downward arc to the maximum feasible value for chairs on the Chairs axis. A production possibilities frontier curve of Couches versus Chairs is a straight line that connects the maximum feasible value for couches on the Couches axis to the maximum feasible value for chairs on the Chairs axis. Refer to Figure 3-1. The rate of trade-off between producing chairs and producing couches is constant in a. neither Graph (a) nor Graph (b). b. both Graph (a) and graph (b). c. Graph (a) only. d. Graph (b) only