Encode and Decode Messages
-Use the Coding Matrix $A = \left[ \begin{array} { r r } 1 & - 4 \\ - 2 & 9 \end{array} \right]$

Multiple Choice

Encode and Decode Messages
-Use the coding matrix $A = \left[ \begin{array} { r r } 1 & - 4 \\ - 2 & 9 \end{array} \right]$ and its inverse $A ^ { - 1 } = \left[ \begin{array} { l l } 9 & 4 \\ 2 & 1 \end{array} \right]$ to decode the cryptogram $\left[ \begin{array} { r r } - 7 & - 8 \\ 16 & 21 \end{array} \right]$ .

A) ABLE
B) ACTS
C) ARMS
D) ALAS