At a math conference, the following exchange rates are used:\ \qquad 1 calculator = 100 rulers\ \qquad 10 rulers = 30 compasses\ \qquad 25 compasses = 50 protractors\How many protractors are equivalent to 1 calculator?
Answer Choices
A. 400
B. 600
C. 300
D. 500
E. 200