$4-12$ Because the rinse water flow rate for a nickel plating bath $($Problem $4-11)$ is quite high, it is proposed that the countercurrent rinse system shown in Figure P$-4-12$ be used to reduce the flow rate. Assuming that the $C_n$ concentration remains the same at $28mg*L^{-1},$ estimate the new flow rate. Assume that the rinse tank is completely mixed and that no reactions take place in the rinse tank.