Half of the class were given pens and were asked what is the maximum price at which they would be willing to buy them. The prices they gave were: $0, $1, $0, $1. The other half of the class did not receive pens and were asked what is the minimum price that they would be willing to sell the pens for. The prices they gave were: $6, $5, $10, $5. Which of the behavioural phenomena that we learned about in the class could explain the stark differences in valuation? Write the general form of the utility function for those who got the pen and those who did not get the pen and draw a graph to help you answer the question.