Asafa ran at a speed of 21\:km/h from P to Q to R to S, as shown. Florence ran at a constant speed from P directly to R and then to S. They left P at the same time and arrived at S at the same time. How many minutes after Florence did Asafa arrive at point R?
Answer Choices
A. 0
B. 8
C. 6
D. 7
E. 5