John has decided to move to Melbourne and study full time at Swinburne. The cost of tuition and textbooks totals $20,000 a year, and John will have to pay $10,000 for accommodation. Should John decide not to study, he would have two other options. He could stay home with his parents (rent-free), work for the family business and earn $40,000 a year. Else he could move to Sydney, work in a friend's start-up company and make $50,000. Rent in Sydney will cost him $15,000.

What would be the opportunity cost of John going to university? Please include your calculations.