Estonian Mathematical Olympiad

The letters $M$, $A$, $T$, $E$, $I$ and $K$ are assigned the numbers $1$, $2$, $3$, $4$, $5$ and $6$ in a certain order so that different letters correspond to different numbers. The sum of the numbers corresponding to the letters of the word $MATEMAATIK$ (taking into account repetitions) is $42$ and the sum of the numbers corresponding to the letters of the word $KEEMIK$ (taking into account repetitions) is $13$. Find the sum of the numbers corresponding to the letters of the word $IT$.