At their usual efficiency levels, A and B together finish a task in 12 days. If A had worked half as efficiently as she usually does, and B had worked thrice as efficiently as he usually does, the task would have been completed in 9 days. How many days would A take to finish the task if she works alone at her usual efficiency?
A) 36
B) 18
C) 24
D) 12
E) 30![]()
A) 36
B) 18
C) 24
D) 12
E) 30