Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[Q]: Problem: at joes steakhouse the hourly wage for a chef is 20 % greater than that of a dishwasher, and the hourly wage of a dishwasher is half as much as the hourly wage of a manager. if a managers wage is $ 6.50 per hour, how much less than a manager does a chef earn each hour ?
Options: a. $ 2.6, b. $ 2.40, c. $ 3.40, d. $ 4.40, e. $ 5.40
[A]: a


[Q]: Problem: a man ' s speed with the current is 18 km / hr and the speed of the current is 2.5 km / hr. the man ' s speed against the current is ?
Options: a. 10, b. 18, c. 50, d. 30, e. 40
[A]: b


[Q]: Problem: a cistern is filled by pipe a in 12 hours and the full cistern can be leaked out by an exhaust pipe b in 18 hours. if both the pipes are opened, in what time the cistern is full ?
Options: a. 50 hrs, b. 60 hrs, c. 36 hrs, d. 80 hrs, e. 90 hrs
[A]:
c