A tank with a volume of 30 cubic feet has one inlet pipe and 2 outlet pipes. The inlet pipe fills water into the tank at the rate of 3 cubic inches/min and the 2 outlet pipes empty it out at the rates of 12 cubic inches/min and 6 cubic inches/min respectively. If all 3 pipes are opened when the tank is full, how many minutes does it take to empty the tank? (1 foot = 12 inches)  Choose the correct choice from the following answers:	A) 2345	B) 3456	C) 4567	D) 5678	E) 6789
The tank is emptied at this rate: 12 + 6 - 3= 
<gadget id="calculator">12 + 6 - 3</gadget>
<output>15</output>
15 cubic inches/min   The tank has a volume of  30*12*12*12= 
<gadget id="calculator"> 30*12*12*12</gadget>
<output>51_840</output>
51840 cubic inches.   The time it takes to empty the tank is 51840/15= 
<gadget id="calculator">51840/15</gadget>
<output>3_456</output>
3456 minutes.   The answer is 3456.
<result>B</result>
A tank with a volume of 30 cubic feet has one inlet pipe and 2 outlet pipes. The inlet pipe fills water into the tank at the rate of 3 cubic inches/min and the 2 outlet pipes empty it out at the rates of 12 cubic inches/min and 6 cubic inches/min respectively. If all 3 pipes are opened when the tank is full, how many minutes does it take to empty the tank? (1 foot = 12 inches)