A tank, containing 480 liters of liquid, has a brine solution entering at a constant rate of 2 liters per minute. The well-stirred solution leaves the tank at the same rate. The concentration within the tank is monitored and found to be

$$c(t) = \frac{e^{\frac{-t}{300}}}{30} \ \ \mathrm{kg/L}.$$

1. Determine the amount of salt initially present within the tank.
   
   Initial amount of salt = kg
   
   
2. Determine the inflow concentration $c_{in}(t)$, where $c_{in}(t)$ denotes the concentration of salt in the brine solution flowing into the tank.
   
   $c_{in}(t) =$ kg / L