1. Using the digraphic cipher that sends the plaintext block $P_{1} P_{2}$ to the ciphertext block $C_{1} C_{2}$ with
$$\begin{array}{l}
C_{1} \equiv 3 P_{1}+10 P_{2} \quad(\bmod 26) \\
C_{2} \equiv 9 P_{1}+7 P_{2} \quad(\bmod 26)
\end{array}$$
encipher the message BEWARE OF THE MESSENGER.
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