What is the opportunity cost of producing one additional arepa when moving from Point A to Point B? When moving from Point C to Point D?

What is the opportunity cost of producing one additional empanada when moving from Point E to Point D? From Point C to Point B?

Explain whether the opportunity cost of producing an additional arepa increasing, decreasing, or constant. Explain whether the opportunity cost of producing an additional empanada is increasing, decreasing, or constant.

Is the PPF linear, bowed out, or neither?