16. 设

$$
A =\left(\begin{array}{llll}
a_{11} & a_{12} & a_{13} & a_{14} \\
a_{21} & a_{22} & a_{23} & a_{24} \\
a_{31} & a_{32} & a_{33} & a_{34} \\
a_{41} & a_{42} & a_{43} & a_{44}
\end{array}\right), B =\left(\begin{array}{llll}
a_{14} & a_{13} & a_{12} & a_{11} \\
a_{24} & a_{23} & a_{22} & a_{21} \\
a_{34} & a_{33} & a_{32} & a_{31} \\
a_{44} & a_{43} & a_{42} & a_{41}
\end{array}\right), P _1=\left(\begin{array}{llll}
0 & 0 & 0 & 1 \\
0 & 1 & 0 & 0 \\
0 & 0 & 1 & 0 \\
1 & 0 & 0 & 0
\end{array}\right),
$$

$P _2=\left(\begin{array}{llll}1 & 0 & 0 & 0 \\ 0 & 0 & 1 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 0 & 1\end{array}\right)$, 其中 $A$ 可逆, 则 $B ^{-1}$ 等于