Suppose Spain produces only cars and trucks. The resources that are used in the production of these two goods are not specialized-that is, the same set of resources is equally useful in producing both trucks and cars. The shape of Spain's production possibilities frontier (PPF) should reflect the fact that as Spain produces more trucks and fewer cars, the opportunity cost of producing each additional truck ___. The following graphs show two possible PPFs for Spain's economy: a straight-line PPF (PPF_1) and a bowed-out PPF (PPF_2). Suppose Spain produces only cars and trucks. The resources that are used in the production of these two goods are not specialized-that is, the same set of resources is equally useful in producing both trucks and cars. The shape of Spain's production possibilities frontier (PPF) should reflect the fact that as Spain produces more trucks and fewer cars, the opportunity cost of producing each additional truck ___. The following graphs show two possible PPFs for Spain's economy: a straight-line PPF (PPF_1) and a bowed-out PPF (PPF_2)