The formula
A dropped or bonus question is still one of the original 75 questions, so in full-paper mode correct + incorrect + unattempted + bonus must equal 75.
Your raw score is the marks earned on correct responses minus one mark for each incorrect response: score = (correct × 4) − incorrect. Unanswered questions contribute nothing at all, so leaving a question blank is neutral in the arithmetic.
If the final answer key drops a question or awards it to every candidate, those questions are added at the full +4 each: score = (correct × 4) − incorrect + (officialBonusQuestions × 4).
