Casey is pumping water out of her well. She can pump 3 gallons a minute. She has 4 rows of 15 corn plants each, and each plant needs half a gallon of water. She also has 10 pigs, which each need 4 gallons of water, and 20 ducks that each need a quarter of a gallon of water. How many minutes does Casey need to spend pumping water?
Please reason step by step, and put your final answer within \boxed{}.
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