"ou are considering renting a city apartment with 1,000 square feet for $1 comma 200 per month. The monthly rent on a larger, 1,500-square-foot city apartment is $1 comma 700. The marginal cost of renting an apartment with 500 additional square feet is"?

$1 per square foot per month

Explanation:

the marginal cost of renting an apartment with 500 additional square feet = $1,700 - $1,200 = $500 or $1 per square foot per month.

The marginal cost of anything is the cost of purchasing (or leasing or producing) one extra unit of output or product.  This is why the answer must be expressed in the cost of an extra unit, not 500 extra units.

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