Turn b5 & b7 anti-clockwisely for 90 degrees, b6 clockwisely for 90 degrees, and b9 for 180 degrees (i.e. twice 90 degrees either way).
In case anybody need a hint:
The central cell of each block (i.e. r258c258) stay put. That restrict some blocks from turning 90 degrees once. Once you figure out which and how many blocks must turn 90 degrees once (or thrice) you'll know how many blocks must turn 180 degrees. And it's easy to check which blocks must not turn 180 degrees.