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MAT SOLVE <X> FROM <A>*<X>=<B> 
where A is m*n, m>=n and r(A)=n,
      B is m*k
yields the solution X of linear equations (when m=n)
    or the least squares solution X (when m>n).

The algorithm is automatically selected according to the nature of A:
   If A is diagonal, solution is trivial,
   else if A is triangular, straight backsubstitution is used,
   else if A is symmetric, 'choldet1' and 'cholsol1' is used,
   else (when m>=n) 'Ortholin1' is used.
If the columns of A are linearly dependent, an error message will be
displayed. eps=1e-15 is the tolerence limit for 'non-zero' entities.
In this case the singular value decomposition may be used (see SING).

Reference: Wilkinson-Reinsch: Handbook for Automatic Computation,
           Vol.II, Linear algebra.
  N = Solving AX=0 (Finding null space of A) 
  M = More information on MAT operations