Answer:
$3 is Zoe's Bakery marginal cost and Short run profits are $150.
Step-by-step explanation:
As a change in quantity is not specified, then, The Marginal cost is the average variable cost of producing 1 unit ($3). And the profit at 150 units produced and sell at a price of $5 is $150 as revenue is $750 and total cost is $600.