Answer:
The marginal cost is $200 that she needs to complete the task.
Step-by-step explanation:
Giving the following information:
Cassie has just spent $800 purchasing, cleaning, and reconstructing an antique quilt which she expects to sell for $1,500 once she is finished. After having spent $800, Cassie discovers that she would need some special period fabric that would cost her $200 in material and time to complete the task. Alternatively, she can sell the quilt "as is" now for $900.
The $800 is a sunk cost. Now we need to determine the marginal cost. The marginal cost is $200 that she needs to complete the task.