def METHOD_NAME(prefix_str: str, postfix: str) -> float:
    prefix = SimCountPrefix[prefix_str.upper()]
    #  topic = "openWB/" + prefix.topic + ("/WHImported_temp" if postfix == POSTFIX_IMPORT else "/WHExport_temp")
    if prefix.topic == "pv2":
        topic = "openWB/pv" + ("/WH2Imported_temp" if postfix == POSTFIX_IMPORT else "/WH2Export_temp")
    else:
        topic = "openWB/" + prefix.topic + ("/WHImported_temp" if postfix == POSTFIX_IMPORT else "/WHExport_temp")
    mqtt_value = read_mqtt_topic(topic)
    log.info("read from broker: %s=%s", topic, mqtt_value)
    if mqtt_value is None:
        result = None
    else:
        try:
            # MQTT-Value is in Watt-seconds for historic reasons -> / 3600
            result = float(mqtt_value) / 3600
        except ValueError:
            log.warning("Value <%s> from topic <%s> is not a valid number", mqtt_value, topic)
            result = None
    if result is None:
        result = (prefix.read_import if postfix == POSTFIX_IMPORT else prefix.read_export)()
    ramdisk_write(prefix_str + postfix, result)
    return result