Matrix multiplication (20pts)

A=[ a1 a2 ... an]= [ a11 a12 .... a1n; a21 a22 ...a2n; .....]
B=[b1; b2; .....;bn]=[b11 b12 ....; b21 b22.....; bn1 bn2....]

姐係下面2條LINK
http://upload.wikimedia.org/math/a/d/6/ad67996e9dec70cd1564b02808ee0e86.png
http://upload.wikimedia.org/math/6/6/c/66c5844a17f49b58096551eef112b993.png

1.what is the i,jth component of AB in terms of ai,j and bi,j
2. what is the i,jth component of (ak)(bk) in terms of ai,j and bi,j
3. what is AB in terms of ai and bi

另外想問，
B=[0 0 0;0 b b;0 b -b]
what is b, if the rank of B is one