For the red cell in the output (row 0, column 0), we take the red row of the first matrix (row 0) and the red column of the second matrix (column 0), and do a dot product (1*1 + 2*4 + 3*7 + 4*10) to get 70. Likewise, for the green cell in the output (row 1, column 2), we take the green row of the first matrix (row 1) and the green column of the second matrix (column 2), and do a dot product (5*3 +