David is a Canadian resident who works in Canada, where he owns a pizza business. Robert is also Canadian, but he works in the United States. On a typical day, David makes $275 in sales. Robert makes $150 in wages. There are no other costs. Based on this information, compute David and Robert's contributions to the following and explain:
a. Canadian GDP
b. Canadian GNP
c. U.S. GDP
d. U.S. GNP