In a legislative assembly election, a political group hired a public relations firm to promote its candidate in three ways: telephone, house calls, and letters. The cost per contact (in paise) is given in matrix $A$ as

$A = \left[ {\begin{array}{*{20}{c}}
  {\mathrm {Cost\,\,per\,\,contact}} \\ 
  {40} \\ 
  {100} \\ 
  {50} 
\end{array}} \right]\begin{array}{*{20}{l}}
  {{\text{ Telephone }}} \\ 
  {{\text{ Housecall }}} \\ 
  {{\text{ Letter }}} 
\end{array}$

The number of contacts of each type made in two cities $\mathrm{X}$ and $\mathrm{Y}$ is given by

$B=$$\,\left[ {\begin{array}{*{20}{c}}
  {\mathrm {Telephone}}&{\mathrm {Housecall}}&{\mathrm {Letter}} \\ 
  {1000}&{500}&{5000} \\ 
  {3000}&{1000}&{10,000} 
\end{array}} \right]\,$ $\begin{array}{*{20}{c}}
  {} \\ 
  { \to X} \\ 
  { \to \,Y} 
\end{array}$.  Find the total amount spent by the group in the two cities $\mathrm{X}$ and $\mathrm{Y}$.

$A=\left[\begin{array}{l}a_{i j}\end{array}\right]_{m\times n}$ is a square matrix, if

Find $\mathrm{X}$ and $\mathrm{Y}$, if $\mathrm{X}+\mathrm{Y}=\left[\begin{array}{ll}5 & 2 \\ 0 & 9\end{array}\right]$ and $\mathrm{X}-\mathrm{Y}=\left[\begin{array}{cc}3 & 6 \\ 0 & -1\end{array}\right]$.

If $A = \left[ {\begin{array}{*{20}{c}}1&2\\{ – 3}&0\end{array}} \right]$ and $B = \left[ {\begin{array}{*{20}{c}}{ – 1}&0\\2&3\end{array}} \right]$, then