case

1-How do two taxpayers determine who has priority to claim the dependency exemption for a qualifying child of both taxpayers when neither taxpayer is a parent of the child (assume the child does not qualify as a qualifying child of either parent)? How do parents determine who gets to deduct the dependency exemption for a qualifying child of both parents when the parents are divorced or file separate returns?

2-Should the labor we donate when we volunteer be deductible?  How would it be calculated?  What would be the advantages and disadvantages?