The Above Table Shows the Probability Distribution of Cake Sales

The above table shows the probability distribution of cake sales at Busy Betty's Bakery.
-Refer to the table above. Busy Betty sells her cakes for $20 each and her constant marginal cost to produce each cake is $12, which is equal to her (constant) average total cost. If she does not sell a cake the day she makes it, she sells it as day- old cake for $10. What is her expected marginal cost of holding the 20th cake in inventory?

A) $0.20
B) $0.40
C) $10.00
D) $2.00