def supervivencia(df, sex, pclass, edat1, edat2):
    if edat1 >= 0:
        dfs = df[ (df['Sex']==sex) & (df['Pclass']==pclass) &
                  (edat1 <= df['Age']) & (df['Age'] <= edat2) ]
    else:
        dfs = df[ (df['Sex']==sex) & (df['Pclass']==pclass) &
                  (df['Age'].isna()) ]
    npass = len(dfs)
    nsurv = len(dfs[dfs['Survived']]) # Alternativa: nsurv = dfs['Survived'].sum()   
    return npass, nsurv, npass - nsurv 


def preu_max(df, pclass):
    df2 = df[df['Pclass'] == pclass]
    idx = df2['Fare'].idxmax()
    passatger = df2.loc[idx]
    return passatger['Name'], passatger['Fare']