Sam andTracy have been married for 25 years. They have filed a joint return every year of their marriage. They have two sons, Christopher and Zachary. Christopher is 19 years old and Zachary is 14 years old. Christopher lived in his parents' home from January through August and he lived in his own apartment from September through December. During the year, Christopher attended college for one month before dropping out. Christopher's living expenses totaled $12,000 for the year. Of that, Christopher paid $5,500 from income he received while working a part-time job. Sam and Tracy provided the remaining $6,500 of Christopher's support. Zachary lived at home the entire year and did not earn any income. Whom are Sam and Tracy allowed to claim as dependents?