While Working the Evening Shift, Agent K Took 8 Hours

Multiple Choice

While working the evening shift, Agent K took 8 hours to complete a task and Agent M took 10 hours to complete the same type of task. How many hours would it take Agent K and Agent M to complete the same task working together, each working at his own rate?

A) 9
B) 8 1/9
C) 4 4/9
D) 6 3/4
E) None of these