A plant manager has a decision to make. She needs to reduce the concentration of salt in the $8000$gal tank from $30,000m\frac{g}{L}$ to $1500m\frac{g}{L}.$ She can do it in one of two ways: $($I$)$ she can start flushing it out by keeping the tank well mixed while running in a hose with clean water $($zero salt$)$ at a flow rate of $60gpm($with an effluent of $60gpm,$ obviously$)$ or $(2)$ she can empty out some of the saline water and fill it up again with enough clean water to get $1500m\frac{g}{L}.$ The maximum rate at which the tank will empty is $60gpm,$ and the maximum flow of clean water is $60gpm.$ If she intends to do this job in the shortest time possible, which alternative will she choose?