A Question of Timing 2: Communion Master/Slave

[tinkthank]

If commander A casts communion slave in round 1 and commander B casts communion slave in round 2 and commander C casts communion master in round 3, will C be the master of A or B or A and B or none of the above? What if commander D casts slave in round 4 -- will C then be master of all 3? What if commander E casts master in round 5? Basically, wondering if there is a general rule here.... thanks much!