Answer:
Correctly ignored a sunk cost.
Explanation:
In economics a sunk cost is one that an individual has already paid for and cannot recover. For example when payment is made for rent it is no longer recoverable.
In this instance Eric has already bought a $50 ticket that is nonrefundable, nonexchangeable, and nontransferable. This is a sunk cost.
Eric wants to go to the concert with Ginny who he wanted to date for a long time.
He will correctly ignore the sunk cost of going to the play because any more time spent on the play will not help recover the $50 already spent.