A large plumbing system supplied by a 2-inch main contains 10 flush-valve urinals, 20 tank water closets, 25 lavatories (with hot and cold-water supplies), and three drinking fountains. The building owner wants to install an additional 15 flush-valve urinals to the system. What is the maximum number of urinals that can be added to the system without modifying the main? A. 3 C. 10 B. 8 D. 14