$P$ is the product of two matrices, as shown at right. Show each result described below or explain why it cannot be shown.

$P = \left[ \begin{array} { c c c } { 2 } & { - 1 } & { 5 } \\ { - 4 } & { 0 } & { 7 } \end{array} \right] \left[ \begin{array} { c c } { - 3 } & { 2 } \\ { 1 } & { - 6 } \\ { 0 } & { 1 } \end{array} \right]$

1. $P$

   Hint (a):

   Remember to multiply the first matrix's rows by the second's column.

2. $P_{1,2}$

   Hint (b):

   1,2 means row one column two.

3. $P_{2,3}$

   Hint (c):

   See part (b).