If MDS in AES has branch number 5 (so 5 active s-boxes in 2 rounds), wouldn't that mean 4 rounds of AES has $5*2=10$ active s-boxes?
AES paper says it has 25 ($5^2$?) active s-boxes in 4 rounds.
How to calculate minimal active s-boxes from branch number for any given number of rounds?
Edit: J.D. noted that you can't calculate the minimum number of active s-boxes from the branch number of MixColumns, because MixColumns isn't the only operation. So let's assume cipher has full state MDS like SHARK and Khazad.