A4. The final grade for the master's exam is composed of $\frac{2}{5}$ of the theory grade and $\frac{3}{5}$ of the practical grade. The grades range from 1 to 10. Master Jaka mistakenly swapped the grades for the theory and practical parts. As a result, the candidate received a grade that was 1 point higher than they deserved. What could the candidate's actual grades for theory and practice be?
(A) theory 6, practice 7
(B) theory 7, practice 6
(C) theory 4, practice 9
(D) theory 9, practice 4
(E) theory 5, practice 10
A4. The candidate received a score of 9 in theory and 4 in practice, since $\frac{2}{5} \cdot 9+\frac{3}{5} \cdot 4=6$ and $\frac{2}{5} \cdot 4+\frac{3}{5} \cdot 9=7$. In other cases, this does not hold.