A class has 40 students.
• Thirty students are prepared for the exam,
• Ten students are unprepared. The professor writes an exam with
10 questions, some are hard and some are easy.
• 7 questions are easy. Based on past experience, the professor
knows that: – Prepared students have a 90% chance of answering easy
questions correctly – Unprepared students have a 50% chance of
answering easy questions correctly.
• 3 questions are hard. Based on past experience, the...