For a 3*3 matrix, I could only find 25 calls but according to the solution, it should be 2 ^ (3+3) = 64
Remember that we are looking for the Big O notation here. That is the maximum upper bound of the calls. Check out this Wikipedia article for more information.
Big O notation isn’t the upper bound, (at least in computer science usage) it’s the highest term of an equation minus any constants or coefficients.
Are we sure this isn’t O^(R || C)?