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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _Tf(P, S):
 """Procedure to calculate the freezing temperature of seawater Parameters P : float Pressure, [MPa] S : float Salinity, [kg/kg] Returns ------- Tf : float Freezing temperature, [K] References IAPWS, Advisory Note No. 5: Industrial Calculation of the Thermodynamic Properties of Seawater, http://www.iapws.org/relguide/Advise5.html, Eq 12 """

    def f(T):
        T = float(T)
        pw = _Region1(T, P)
        gw = pw["h"]-T*pw["s"]

        gih = _Ice(T, P)["g"]

        ps = SeaWater._saline(T, P, S)
        return -ps["g"]+S*ps["gs"]-gw+gih

    Tf = fsolve(f, 300)[0]
    return Tf