The correct answer is not $20.

The most reasonable choice is zero profit, you end up with the same value of money from what you started with i.e. enough to buy one goat.

>inb4 but you have more money at the end!

More money is not more value. Inflation is not profit, hence why the question is bad and most of /sci/ fell for it. It should be specified whether the values of goat and money went up or down.

Even most of /sci/ can't answer it right, no wonder we're doomed as a society with the current money printing banking system.