At a price of $5, Pat buys 10 units of a product; when the price increases to $6, Pat buys 8 units. Riley says Pat's demand has decreased. Is Riley correct?
a. Yes, Riley is correct. Pat's demand has decreased.
b. No, Riley is incorrect. Pat's quantity demanded has increased, and his demand has increased.
c. No, Riley is incorrect. Pat's demand has increased.
d. No, Riley is incorrect. Pat's quantity demanded has decreased, and his demand has not changed.