A copy machine, working at a constant rate, makes 35 copies per minute. A second copy machine, working at a constant rate, makes 65 copies per minute. Working together at their respective rates, how many copies do the two machines make in half an hour ?	Select the correct option
A) 3,000 B) 2,700 C) 4,500 D) 5,400 E) 324,000

Rationale: "together the two machines make 35 + 65 = 100 copies per minute . so , in half an hour they will make 100 * 30 = 3,000 copies . answer : a ."
Answer: A