Suppose russia produces only trucks and cars. 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 cars and trucks. the shape of russia's production possibilities frontier (ppf) should reflect the fact that as russia produces more cars and fewer trucks, the opportunity cost of producing each additional car

Remains constant

Explanation:

Since the same set of resources are useful in producing both cars and trucks, it shows that resources are not specialized hence Russia has a straight line PPC. A straight line (linear) PPC connotes constant returns to scale. In this case, resources are mobile and can easily be reallocated and redirected from the production  of one good to another thus, opportunity cost is constant and so is the marginal rate of transformation (MRT). The MRT is the number of units or amount of a good that must be foregone in order to attain one unit of another.  If Russia decides to produce more cars and fewer trucks, the resources deployed in producing more cars would be well suited as the resources already used in car production. The opportunity cost in producing each additional unit of car remains constant as more cars are produced.

The slope of a linear PPC determines the marginal rate of transformation; that is, a flatter slope would mean producing more cars requires trading-off fewer trucks while a steeper slope would mean that producing more cars requires trading-off more trucks.