Mqtt automation send value calculation

Configuration
,
1

Hello,
I would like to send sensor.entity.id multiply by 0.7 as payload.
Please help.
Here is my action:
action:

  • service: mqtt.publish
    data:
    topic: Soyosource/SOYO_1e5ac0/MaxPower
    qos: ‘1’
    payload: ‘700.00’
2

Hello @wolf_gi and welcome to the home assistant community :tada:

Please take some minutes of your time on how to ask a good question - or - how to help us help you :point_down: