ere we know neither

nor

but an attack on this cryptosystem told us that the plaintext 'NENAGH' was encrypted as $\text{'}$SGMCRZ$\text{'}.$ i$.$e$.$ NENAGH

SGMCRZ$.$

First find

and

$,$ the private key. Input each matrix entry as an integer between $0$ and $25$ ie a member of

$.$