Arlo and margaret have been married for 30 years. since their children left home, they have nothing to talk about. it is almost like two "strangers" living in the same household, each with his or her own interests. the passion has also waned in their relationship. both have contemplated divorce but have decided to stay married because of their adult children and soon-to-be first grandchild and because it would be too hard to divide their accumulated possessions and to start over again. according to robert sternberg, which type of love do arlo and margaret possess?