True or False

1. If a matrix has 4 rows and 5 columns then the number of elements in that matrix is 9.
2. A square matrix A= [a_{ij}] is called diagonal matrix if a_{ij} =0 for i = j.
3. Identity matrix is not a diagonal matrix.
4. If A= [a_{ij}] _{2x3} and B= [b_{ij}] _{3x4} then order of (AB) is 2x4
5. If all the entries in a matrix are multiplied by scalar k than whole matrix is multiplied by 3k.
6. In (AB) ^{-1}= A^{-1}B^{-1} when A&B are matrices.
7. Inverse of every matrix exist.