Three pencils cost the same as two erasers. Four erasers cost the same as one ruler. Therefore, pencils are more expensive than rulers.

She gives the erasers to Lucy and ________ . A: I B: me C: my D: Mine

A country produces only pencils and erasers. Pencil production is allocatively efficient if the marginal ________ of a pencil equals the marginal ________ of ________. A: cost; benefit; an eraser B: cost; cost; an eraser C: benefit; benefit; an eraser D: benefit; cost; a pencil