A large tanker can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half?

1. A Option A: 15 min
2. B Option B: 20 min
3. C Option C: 27.5 min
4. D Option D: 30 min

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