def derive_ip_address( cidr_block, delegate, final8 ):
    """
        Given a CIDR block string, a delegate number, and an integer
        representing the final 8 bits of the IP address, construct and return
        the IP address derived from this values.  For example, if cidr_block is
        10.0.0.0/16, the delegate number is 10, and the final8 is 8, the
        derived IP address will be 10.0.10.8.
    """
    result = ''
    match = re.match( r'\d+\.\d+', cidr_block )
    if match:
        result = '{}.{}.{}'.format( match.group(0), delegate, final8 )
    else:
        raise SpinupError( "{} passed to derive_ip_address() is not a CIDR block!".format(cidr_block) )

    return result