A study on the sales of Harry Potter books recently concluded that p% were purchased by readers who were 14 years or older. You just surveyed n people who are Harry Potter book owners and you found that, on average, 18 of them were 14 years or older, with a variance of 7.2. What is the value of n, and what percentage of Harry Potter book sales were purchases by readers who were under the age of 14 (answers are in that order)?
A. 30; 40%
B. 45; 40%
C. 30; 60%
D. 45; 60%