Matrices & Systems · Medium problem

A simple cipher encodes a pair of letter-codes $(x,y)$ (each $0$-$25$) as $K\begin{pmatrix}x\\y\end{pmatrix} \bmod 26$, using the key $K = \begin{pmatrix}3 & 2\\5 & 7\end{pmatrix}$. Encode the pair T, E, that is $(x,y) = (19, 4)$ (T is the $20$th letter, code $19$; E is the $5$th, code $4$). Give the SECOND encoded value (after reducing mod $26$).