Manuel has plans to go to a movie and already has a $10 nonrefundable, nonexchangeable, and nontransferable ticket. Now Poornima, whom Manuel has wanted to date for a long time, asks him to a concert. Manuel would prefer to go to the concert with Poornima and forgo the movie, but he doesn't want to waste the $10 he spent on the movie ticket.

From the perspective of an economist, if Manuel decides to go to the movie, what has he just done?

1. Incorrectly allowed a sunk cost to influence his decision
2. Made an optimal choice
3. Correctly ignored a sunk cost

Sunk costs refer to those costs which have been incurred in the past and which can no longer be recovered. For example, past expenditure on research and development with no current or future benefits represent sunk costs which can no longer be recovered.

Sunk costs are irrelevant for decision making process as they do not relate to current projects and yield no economic benefit.

In the given case, Manuel had already purchased a $10 movie ticket, which can neither be transferred nor eligible for a refund. Later when he does not exercise the option of going for the movie and opts for a concert instead, the amount of 10$ spent on the movie represents a sunk cost which is non recoverable.