By how much would GDP change as a result of each of the following changes? (a) A parent switches from buying pre-made ham and cheese sandwiches for a family dinner, which would have cost $20, to buying the raw ingredients, which cost only $6, and making the same ham and cheese sandwiches at home. (b) A woman marries her butler, whom she formerly paid $50,000 a year. After they are married, her husband continues to wait on her as before, but as a husband rather than an employee.