Answer:
D- The proportion of PXC computers bought by first-time computer buyers was smaller last year than the previous year.
Explanation:
Considering the number of computers sold were about the same amount both last year and the previous year by PXC, according to the facts stated, an increase in profit would have been brought about by a change in the proportion of first time buyers and buyers looking for replacements.
The number of first time buyers, was substantially reduced compared to the number of buyers looking to replace their old computers, who buy more expensive models of PXC computers. This change in proportion caused a change in the profit margin of the company as more units with higher profit margins were purchased last year.