CAYLEY 2008 Problem 17

If 3\le p\le10 and 12\le q\le21, then the difference between the largest and smallest possible values of \displaystyle\frac pq is

Answer Choices
A. \frac{29}{42}
B. \frac{29}{5}
C. \frac{19}{70}
D. \frac{19}{12}
E. \frac{19}{84}