Jeff and Ursula each run 30\:km. Ursula runs at a constant speed of 10\:km/h. Jeff also runs at a constant speed. If Jeff’s time to complete the 30\:km is 1 hour less than Ursula’s time to complete the 30\:km, at what speed does Jeff run?
Answer Choices
A. 6\:km/h
B. 11\:km/h
C. 12\:km/h
D. 15\:km/h
E. 22.5\:km/h