Matrix multiplication
Let A be an m?k matrix and B be a k ?n matrix. The product of
A and B, denoted by AB, is the m?n matrix [cij] such that
cij = ai1b1j + ai2b2j + … + aikbki
(to compute cij, multiply the first element of the ith row of A by the first
element of the jth column of B, multiply the second element of the ith
row of A by the second element of the jth column of B, … and add all