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