Cristina is a freelance graphic designer. She earns on average $45 per hour and has no problem getting new clients and take on more work. She’s been working hard and has gotten tired, so she decides to take a break and go to a rock concert. She gets a ticket for $70 and expects to spend additional $15 on snacks and drinks. It will take her 4 hours and $4 worth of gas to get to the venue, attend the concert, and come back. What is Cristina’s opportunity cost of going to the concert? $