The profileration of the internet has given rise to a new method of advertising, called spamming, that essentially is a more cost-effective method of the telephone solicitations method known as cold calling. If a company buys three mailing list with 2,500, 3,500, and 4,000 email addresses respectively and spam them with promotional material, how many potential customers has it reached?

A. 5,000
B. 10,000
C. 15,000
D. 20,000