Susan switches from going to Speedy Lube for an oil change to changing the oil in her car herself. Which of the following is correct? The value of changing the oil is
a. included in GDP whether Susan pays Speedy Lube to change it or changes it herself.
b. included in GDP if Susan pays Speedy Lube to change it but not if she changes it herself.
c. included in GDP if Susan changes it herself, but not if she pays Speedy Lube to change it.
d. not included in GDP whether Susan pays Speedy lube to change it or she changes it herself.