Monster rank after combining?

If I combine an A rank monster with an S rank, will the resulting monster be S or A? Or is there a chance of both?

The theory is 50% A rank 50% S rank.

But I had this situation for >5 times and every time I got the higher rank.

I have fused several times, and I got S/A almost every time. I say almost because I am unsure. I think that it was very time though

Moved to FAQ section. 

That’s happened to me every time to. Good thing it worked out that way or I would have wasted a high level Knighthawk

I mixed a A rank with a S rank and got a S but i say A or S are good either way