A team sells tickets to their event and souvenir shirts. There is no marginal cost per ticket, but shirts cost $5 to produce. There are casual fans, who place a value of $10 on tickets and $10 on shirts, and serious fans, who place a value of $26 on tickets and $3 on a t-shirt.
The team sells tickets as a mixed bundle, pricing a ticket and shirt combination at $20. If they want to maximize profits, how much should they charge for a ticket on its own?