Problem with $2-$letter units in an affine encryption system. All these problems can be solved by hand.

All arithmetic is performed in $Z_{26}.x$ below is a $21$ matrix, as is $,$ while $$ is a $22$ matrix.

Encryption function: $f_E(x)=x+mod26$

In this problem, neither $$ nor $$ are known to us but we made an attack on this cryptosystem and discovered that the plaintext 'SODIUM' is encrypted as

'YZUCIX'. That is$,$ SODIUM $f_E$ YZUCIX.

Decrypt 'VIEHSS' in this affine system. VIEHSS $f_D$

$($input a $6-$letter string as your answer: $2+2+2)$