Function that places a 2D matrix B into a larger 2D matrix A. The upper-left corner of B is placed at coordinates (r,c) in A. If (r,c) are not given, then B is put in the upper-left corner of A, a default of (1,1). Some error checking is done first to make sure that A and B are 2D matrices, A is big enough to contain B, and the given (r,c) will not spill B outside of A.
The screenshot results from calling: