Rate

Given that a water tank for irrigation has a volume of \(330\) litres, with a water tap that fills water into the tank at a rate of \(15\) litres per minute, and a water drain that can drain water at a rate of \(30\) litres per minute during irrigation. Find

1. The amount of time it takes (in minutes) for the tank to be filled with water from empty to full when the water drain is blocked,
2. The amount of time it takes (in minutes) for the tank to be drained from full to empty when the water tap is turned off,
3. The amount of time it takes (in minutes) for the tank to be drained from full to empty when the water tap is turned on,
4. To improve the efficiency of irrigation, a new water drain is installed, which works together with the old one. Given that it now takes \(10\) minutes for the tank to be drained from full to empty if both water drains work together when the water tap is turned on, find the rate of drainage of the new water drain.