Tank holds 22k gal of water, with an inflow pipe that allows 240 gal to flow into the tank each minute & an outflow pipe that empties 320 gal of water from the tank each min. If the tank is full, water in the tank, W (m) in gallons, m minutes since both pipes have been opened. The point (160, 9200) on the graph. How many minutes was the tank half empty?
