Consider a market where there are many firms with different cost structures. When determining which firms enter the market first, we look at . A. marginal cost. B. fixed costs. C. average total cost. D. average variable cost. The last firm to enter earns . A. average economic profits. B. positive economic profits. C. zero economic profits. D. the greatest economic profits. If demand shifts to the left (decreases), the last firm that entered .

C. average total cost.

C. zero economic profits.

If demand shifts to the left (decreases), the last firm that entered "earns negative economic profits and so exits the market".

Explanation:

When many firms produces same product with different cost structures, their average total cost of unit cost is used to determining which firms enter the market first because by definition, average total cost or unit cost is equal to total cost divided by the number of units of a goods manufactured by the producer. It is also equal to the sum of average variable costs and average fixed costs. It may be time dependent. So, the lesser the cost of production per unit quantity, the higher the volume produced and the fasters the product enters market.

The last firm to enter earns "zero economic profits" because obviously, the market must have been fully saturated with the products and as at the time the products enters, the satisfaction might have been dropping and people may not buy as before. Other reason for zero economic profits is that such firm products will surely have higher unit cost which will eventually translate to higher price of the products and no one will leave cheaper products of same quality and satisfaction for the one higher price.

If demand shifts to the left (decreases), the last firm that entered "earns negative economic profits and so exits the market" - there are many reasons for a decreasing demands ranging from diminishing satisfaction derived from the products, and so on, the last firm will definitely suffered negative economic profits because the capital involved in cost of production will not even be recovered not to even talk of the profits from the business and this in turn weaken the manufactured from producing more of the products since the goal is not achieved and the products exit market.

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