Costs that spill over to third parties are called

Given that Sandy can produce 10 economics reports or make 2 sales calls and Tim can produce 2 economics reports or make 1 sales call, we can conclude that

A) Sandy should specialize in economics reports, and Tim should specialize in sales calls. B) Sandy should produce both economics reports and sales calls since she cannot possibly gain from trade with Tim. C) Tim should specialize in producing economics reports, and Sandy should specialize in producing sales calls. D) Tim should produce both economics reports and sales calls.

Why should the GDP accounts matter to the average citizen?