Help with some suggestions for Logic

I’m trying to get some ideas for the logic gate for I can do the PLC after ….

Let’s say I have 3 motors, Motor A, Motor B and Motor C “All could be online, offline”
If I turn-on Motor B first, it is going to be Primary motor.

And If I turn on Motor C next, it is going to be Secondary

And if I turn on Motor A, it should be Tertiary..

If Motor C turned off then Motor A should become Secondary and Motor C will be tertiary even if it is in OFF mode and so on ….

I will have six scenarios

Motor A Motor B Motor C
Primary Secondary Tertiary
Primary Tertiary Secondary
Secondary Primary Tertiary
Secondary Tertiary Primary
Tertiary Primary Secondary
Tertiary Secondary Primary

PLC brand/type?

some hints to get you started, post your thinking and any partial work and we'll help you through it.

hints: you need a way to keep track of starting sequence. Write this logic out in any language or diagram of your choosing then translate it to ladder.