Given: y = 628 - 4x A yoghurt tank has a volume of 628 litres when it is full. However, this tank develops a leak and the contents drain out at a rate of 4 litres per minute. The formula above represents the amount of yoghurt inside the tank where x is the time in minutes. 17.1 How long will it take for the tank to empty? (2) 17.2 Determine how much yoghurt will be in the tank 49 minutes after the leak developed.​