Choose the correct answer and explain

Martha is willing to buy 40 cakes from it's supplier at 10$, and she is willing to sell it at $15. Unexpectedly, Martha only receives 36 cakes to be sold in the market. Assuming each customer are willing to pay $20 for each cake. What is Martha's surplus?

$720

$360

$440

$600

$800

Martha is willing to buy 40 cakes from it's supplier at 10$, and she is willing to sell it at $15. Unexpectedly, Martha only receives 36 cakes to be sold in the market. Assuming each customer are willing to pay $20 for each cake. What is the total Martha's consumer surplus?

$720

$360

$440

$600

$800