A certain mixing tank has a capacity of 20 gallons and it is full of water with a small amount of bleach. The concentration of bleach in the tank is %2 initially. At time t=0 pipes which pump water in and out at a rate of 2 gallons per minute are activated (so the volume inside the tank stays the same). The water coming in has a bleach concentration of 10%. Find the amount of bleach inside the tank at time t.