Sylvia is somewhat dissatisfied with her friendship with sarah, in part because sarah has been depressed a lot lately and isn't as much fun to be around any more. sylvia maintains her friendship with sarah in spite of these reservations, in part because she feels that over the years she has known sarah, sarah has been there when sylvia needed her and they have a lot of history together. according to social exchange theory, which of the following best explains why sylvia continues to be friends with sarah?
a forecasted rewards b cumulative rewards c immediate rewards d expected rewards