Len and Krista have a 5-month old baby, Henry. Krista takes care of him during the day, and Len is responsible for his well-being at night. Henry sleeps well at night if he gets good naps during the day - however, if he is overtired by the time his evening bedtime rolls around, he wakes up several times during the night and is hard to soothe. In turn, if he wakes up during the night, then Krista has a harder time with his routine the following day. From the perspective of social interdependence theory, Len and Krista's relationship can be described as: a. competitive b. individualistic c. dependent O d. cooperative