A consumer is willing to trade 3 units of x for 1 unit of y when she has 6 units of x and 5 units of why. Also, she is willing to trade 6 units of x for 2 units of y when she has 12 units of x an 3 units of y. She is indifferent between bundle (6,5) and (12,3). What is the utility function for goods x and y?

Points: (6,5), (12,3), (3,6)