What is a productively efficient point on a PPF?

Given a PPF where the marginal cost of producing an additional unit of good X is 4 units of good Y, and the marginal benefit of good X is 4 units of good Y, what is the allocatively efficient point?

What is a productively efficient point on a PPF?

Allocative efficiency is achieved when:

What does the outward bow shape of a Production Possibilities Frontier (PPF) indicate?

Why can't marginal benefit be derived directly from a PPF?

Why can't marginal benefit be derived directly from a PPF?

Given a PPF where the marginal cost of producing an additional unit of good X is 5 units of good Y, and the marginal benefit of good X is 5 units of good Y, what is the allocatively efficient point?

If moving from 3 to 4 units of good A on a PPF results in a decrease from 8 to 4 units of good B, what is the marginal opportunity cost of the fourth unit of good A?

In a scenario where a city must decide between building a new park or a new library, the marginal cost of the park is \$500,000 and the marginal benefit is \$600,000, while the library's marginal cost is \$400,000 and the marginal benefit is \$350,000. Which project should the city choose based on allocative efficiency?