B | X1 | X2 | ⋯ | Xm |
X1 | c11 | c21 | ⋯ | c1m |
X2 | c21 | c22 | ⋯ | c2m |
⋮ | ⋮ | ⋮ |
| ⋮ |
Xm | cm1 | cm2 | ⋯ | cmm |