def fn(dframe):
    if dframe['A'] < 125:
        return 935 + 0.2 * dframe['A']

    elif (dframe['A'] >= 955) and (dframe['A'] <= 974):
        return 921.2 + 0.2 * (dframe['A'] - 955)

    elif (dframe['A'] >= 975) and (dframe['A'] <= 1023):
        return 925.2 + 0.2 * (dframe['BCCH'] - 975)

    elif (dframe['A'] >= 511) and (dframe['A'] <= 885):
        return 1805.2 + 0.2 * (dframe['A'] - 512)