Sam bicycles at 16\:km/h and Chris bicycles at 24\:km/h. At noon, Sam is 1\:km north of Chris, and each begins to ride north. How many minutes will it take for Chris to catch Sam?
Answer Choices
A. 1\frac12
B. 2\frac12
C. 3\frac34
D. 7\frac12
E. 8