Let $A$ be a matrix of order $3\times 4$. If $R_1$ denotes the first row of $A$ and $C_2$ denotes its second column, then determine the orders of matrices $R_1$ and $C_2$.

Construct a $2\times 3$ matrix whose elements $A=\left[a_{ij}\right]$ are given by :

$a_{ij}=i\times j$

Construct a $2\times 3$ matrix whose elements $A=\left[a_{ij}\right]$ are given by :

$a_{ij}=2i-j$

Construct a $2\times 3$ matrix whose elements $A=\left[a_{ij}\right]$ are given by :

$a_{ij}=i+j$

Construct a $2\times 3$ matrix whose elements $A=\left[a_{ij}\right]$ are given by :

$a_{ij}=\frac{(i+j{)}^2}{2}$

Construct a $2\times 2$ matrix whose elements are given by:

$a_{ij}=\frac{{\left(i+j^{}\right)}^2}{2}$

Construct a $2\times 2$ matrix $A=\left[a_{jj}\right]$ whose elements $a_{ij}$ are given by:

$a_{ij}=\frac{(i-j{)}^2}{2}$

Construct a $2\times 2$ matrix $A=\left[a_{ij}\right]$ whose elements $a_{ij}$ are given by:

$a_{ij}=\frac{(2i+j{)}^2}{2}$