The market value of which of the items would be considered double (or multiple) counting in the calculation of gdp?

a. a used skateboard you buy for your brother
b. the commission paid to the seller of a previously owned collectors skateboard
c. a new building for tony hawk industries
d. used copy of the tony hawk video game
e. previously owned collectors skateboard
f. ticket for the x games bought from a person on a street corner
g. new skateboard you buy for your niece
h. wheels used to produce a skateboard that will be sold new

Penny poodle wanted to know which dog obedience training program was more effective: puppy pride, the approach she has been using for any years, or doggie do-right, a new approach. penny convinced 50 human companions of untrained dogs to participate in her study. the dogs and their humans were randomly assigned to complete the puppy pride or doggie do-right course. at the end of the training programs, all of the dogs were scored on their level of obedience on a standardized dog obedience checklist (scores could range from 10 to 100). the design of this study is: