\left(c_{i1},c_{i2},\ldots,c_{ik}\right)=\left(\sum\limits_{l=1}^{n}{a_{il}b_{l1}},\sum\limits_{l=1}^{n}{a_{il}b_{l2}},\ldots,\sum\limits_{l=1}^{n}{a_{il}b_{lk}}\right)=\sum\limits_{l=1}^{n}\left[a_{il}\left(b_{l1},b_{l2},\ldots,b_{lk}\right)\right]