Implement exam scoring service

src/main/java/com/example/questionbank/service/quiz/ExamScoringService.java

@@ -0,0 +1,15 @@
+package com.example.questionbank.service.quiz;
+
+import com.example.questionbank.domain.enumeration.OptionKey;
+import org.springframework.stereotype.Service;
+
+@Service
+public class ExamScoringService {
+
+    public ScoringResult score(OptionKey correctOption, OptionKey selectedOption) {
+        boolean correct = selectedOption != null && selectedOption == correctOption;
+        return new ScoringResult(correct, correct ? 1 : 0);
+    }
+
+    public record ScoringResult(boolean correct, int awardedPoints) {}
+}