You have won a free ticket to see a Charlie Parr concert (which has no resale value). Ewan Dobson is performing on the same night and is your next best alternative activity. Tickets to see Dobson cost $20. On any given day, you would be willing to pay up to $50 to see Dobson. Assuming there is no other costs of seeing either performance, what is your opportunity cost of seeing Charlie Parr? Explain.