3 pumps, working 8 hours a day, can empty a tank in 2 days. How many hours a day should 4 pumps work in order to empty the tank in 1 day?

3 pumps, can empty a tank in 2 days by working 8 hours a day.
1 pumps, can empty a tank in 2 days by working 8 x 3 hours a day.
1 pumps, can empty a tank in 1 days by working 8 x 3 x 2hours a day.
4 pumps, can empty a tank in 1 days by working 8 x 3 x 2 / 4 hours a day.
4 pumps, can empty a tank in 1 days by working 2 x 3 x 2 hours a day.
4 pumps, can empty a tank in 1 days by working 12 hours a day.