def getBasics(header):
    """
    Return basic information from the header:

        1. bias
        2. gain
        3. readout noise

    :Note: This function is useful for ACS WFC polarimetry data.

    :return: bias, gain, readnoise
    :rtype: list
    """
    bias = header['CCDOFSTB']
    gain = header['CCDGAIN']
    readnoise = header['READNSEB']
    return bias, gain, readnoise