In Cambridge, there are individuals from three different citizenships: Ethiopians, Brazilians, and Americans. Coffee is only sourced from Brazil and Ethiopia. Brazilians and Ethiopians only like to drink coffee from their own country, while for Americans a cup of coffee is the same regardless from its origin (Brazil or Ethiopia). All of them have the same level of income denoted byI

and

is some coefficient greater than0

.

What is a utility function for Americans?