Chris and Pat go on a 30\:km run. They both usually run at 10\:km/h. If Chris runs at \frac12 his usual running speed, and Pat runs at 1\frac12 times her usual speed, how many more hours does it take Chris to complete the run than it takes Pat to complete the run?
Answer Choices
A. 1
B. 1.5
C. 2
D. 4
E. 6